From 4345f8da4106bc1733f05566169eb209c9d3410e Mon Sep 17 00:00:00 2001
From: dotasek <david.otasek@smilecdr.com>
Date: Fri, 19 Jul 2024 11:21:51 -0400
Subject: [PATCH] Return null for all toCode enum params that are Enum.NULL
 (dstu2016may)

---
 .../hl7/fhir/dstu2016may/model/Account.java   |   6 +-
 .../dstu2016may/model/ActionDefinition.java   |  24 +++--
 .../hl7/fhir/dstu2016may/model/Address.java   |  12 ++-
 .../dstu2016may/model/AllergyIntolerance.java |  36 ++++---
 .../fhir/dstu2016may/model/Appointment.java   |  18 ++--
 .../fhir/dstu2016may/model/AuditEvent.java    |  18 ++--
 .../hl7/fhir/dstu2016may/model/Bundle.java    |  18 ++--
 .../hl7/fhir/dstu2016may/model/CarePlan.java  |  18 ++--
 .../org/hl7/fhir/dstu2016may/model/Claim.java |  12 ++-
 .../dstu2016may/model/ClinicalImpression.java |   6 +-
 .../fhir/dstu2016may/model/CodeSystem.java    |  12 ++-
 .../fhir/dstu2016may/model/Communication.java |   6 +-
 .../model/CommunicationRequest.java           |   6 +-
 .../model/CompartmentDefinition.java          |   6 +-
 .../fhir/dstu2016may/model/Composition.java   |  12 ++-
 .../hl7/fhir/dstu2016may/model/Condition.java |   6 +-
 .../fhir/dstu2016may/model/Conformance.java   |  72 ++++++++-----
 .../fhir/dstu2016may/model/ContactPoint.java  |  12 ++-
 .../fhir/dstu2016may/model/DataElement.java   |   6 +-
 .../fhir/dstu2016may/model/DetectedIssue.java |   6 +-
 .../hl7/fhir/dstu2016may/model/Device.java    |   6 +-
 .../dstu2016may/model/DeviceComponent.java    |   6 +-
 .../fhir/dstu2016may/model/DeviceMetric.java  |  30 ++++--
 .../dstu2016may/model/DeviceUseRequest.java   |  12 ++-
 .../dstu2016may/model/DiagnosticOrder.java    |  12 ++-
 .../dstu2016may/model/DiagnosticReport.java   |   6 +-
 .../dstu2016may/model/DocumentReference.java  |   6 +-
 .../dstu2016may/model/ElementDefinition.java  |  30 ++++--
 .../hl7/fhir/dstu2016may/model/Encounter.java |  18 ++--
 .../fhir/dstu2016may/model/Enumerations.java  | 102 ++++++++++++------
 .../fhir/dstu2016may/model/EpisodeOfCare.java |   6 +-
 .../model/FamilyMemberHistory.java            |   6 +-
 .../org/hl7/fhir/dstu2016may/model/Flag.java  |   6 +-
 .../org/hl7/fhir/dstu2016may/model/Goal.java  |   6 +-
 .../org/hl7/fhir/dstu2016may/model/Group.java |   6 +-
 .../dstu2016may/model/GuidanceResponse.java   |   6 +-
 .../dstu2016may/model/HealthcareService.java  |   6 +-
 .../hl7/fhir/dstu2016may/model/HumanName.java |   6 +-
 .../fhir/dstu2016may/model/Identifier.java    |   6 +-
 .../dstu2016may/model/ImagingExcerpt.java     |   6 +-
 .../fhir/dstu2016may/model/ImagingStudy.java  |   6 +-
 .../model/ImplementationGuide.java            |  12 ++-
 .../hl7/fhir/dstu2016may/model/Linkage.java   |   6 +-
 .../fhir/dstu2016may/model/ListResource.java  |  12 ++-
 .../hl7/fhir/dstu2016may/model/Location.java  |  12 ++-
 .../hl7/fhir/dstu2016may/model/Measure.java   |  24 +++--
 .../fhir/dstu2016may/model/MeasureReport.java |  12 ++-
 .../org/hl7/fhir/dstu2016may/model/Media.java |   6 +-
 .../model/MedicationAdministration.java       |   6 +-
 .../dstu2016may/model/MedicationDispense.java |   6 +-
 .../dstu2016may/model/MedicationOrder.java    |   6 +-
 .../model/MedicationStatement.java            |   6 +-
 .../fhir/dstu2016may/model/MessageHeader.java |   6 +-
 .../dstu2016may/model/ModuleMetadata.java     |  24 +++--
 .../fhir/dstu2016may/model/NamingSystem.java  |  12 ++-
 .../hl7/fhir/dstu2016may/model/Narrative.java |   6 +-
 .../dstu2016may/model/NutritionOrder.java     |   6 +-
 .../fhir/dstu2016may/model/Observation.java   |  12 ++-
 .../model/OperationDefinition.java            |  12 ++-
 .../dstu2016may/model/OperationOutcome.java   |  12 ++-
 .../fhir/dstu2016may/model/OrderResponse.java |   6 +-
 .../hl7/fhir/dstu2016may/model/Patient.java   |   6 +-
 .../hl7/fhir/dstu2016may/model/Person.java    |   6 +-
 .../hl7/fhir/dstu2016may/model/Procedure.java |   6 +-
 .../dstu2016may/model/ProcedureRequest.java   |  12 ++-
 .../dstu2016may/model/ProcessRequest.java     |   6 +-
 .../hl7/fhir/dstu2016may/model/Protocol.java  |  18 ++--
 .../fhir/dstu2016may/model/Provenance.java    |   6 +-
 .../hl7/fhir/dstu2016may/model/Quantity.java  |   6 +-
 .../fhir/dstu2016may/model/Questionnaire.java |  12 ++-
 .../model/QuestionnaireResponse.java          |   6 +-
 .../dstu2016may/model/ReferralRequest.java    |  12 ++-
 .../dstu2016may/model/SearchParameter.java    |   6 +-
 .../hl7/fhir/dstu2016may/model/Sequence.java  |   6 +-
 .../org/hl7/fhir/dstu2016may/model/Slot.java  |   6 +-
 .../hl7/fhir/dstu2016may/model/Specimen.java  |   6 +-
 .../model/StructureDefinition.java            |  18 ++--
 .../fhir/dstu2016may/model/StructureMap.java  |  30 ++++--
 .../fhir/dstu2016may/model/Subscription.java  |  12 ++-
 .../dstu2016may/model/SupplyDelivery.java     |   6 +-
 .../fhir/dstu2016may/model/SupplyRequest.java |   6 +-
 .../org/hl7/fhir/dstu2016may/model/Task.java  |  12 ++-
 .../fhir/dstu2016may/model/TestScript.java    |  24 +++--
 .../hl7/fhir/dstu2016may/model/Timing.java    |  12 ++-
 .../dstu2016may/model/TriggerDefinition.java  |   6 +-
 .../hl7/fhir/dstu2016may/model/ValueSet.java  |   6 +-
 .../dstu2016may/model/VisionPrescription.java |  12 ++-
 .../codesystems/AbstractTypesEnumFactory.java |   6 +-
 .../codesystems/AccountStatusEnumFactory.java |   6 +-
 .../ActionBehaviorTypeEnumFactory.java        |   6 +-
 .../ActionCardinalityBehaviorEnumFactory.java |   6 +-
 .../ActionGroupingBehaviorEnumFactory.java    |   6 +-
 .../ActionParticipantTypeEnumFactory.java     |   6 +-
 .../ActionPrecheckBehaviorEnumFactory.java    |   6 +-
 .../ActionRelationshipAnchorEnumFactory.java  |   6 +-
 .../ActionRelationshipTypeEnumFactory.java    |   6 +-
 .../ActionRequiredBehaviorEnumFactory.java    |   6 +-
 .../ActionSelectionBehaviorEnumFactory.java   |   6 +-
 .../codesystems/ActionTypeEnumFactory.java    |   6 +-
 .../codesystems/ActionlistEnumFactory.java    |   6 +-
 ...ActivityDefinitionCategoryEnumFactory.java |   6 +-
 .../AdditionalmaterialsEnumFactory.java       |   6 +-
 .../codesystems/AddressTypeEnumFactory.java   |   6 +-
 .../codesystems/AddressUseEnumFactory.java    |   6 +-
 .../codesystems/AdjudicationEnumFactory.java  |   6 +-
 .../AdjudicationErrorEnumFactory.java         |   6 +-
 .../AdjudicationReasonEnumFactory.java        |   6 +-
 .../AdministrativeGenderEnumFactory.java      |   6 +-
 ...AllergyIntoleranceCategoryEnumFactory.java |   6 +-
 ...ergyIntoleranceCriticalityEnumFactory.java |   6 +-
 .../AllergyIntoleranceStatusEnumFactory.java  |   6 +-
 .../AllergyIntoleranceTypeEnumFactory.java    |   6 +-
 .../codesystems/AnimalBreedsEnumFactory.java  |   6 +-
 .../AnimalGenderstatusEnumFactory.java        |   6 +-
 .../codesystems/AnimalSpeciesEnumFactory.java |   6 +-
 .../AnzscoOccupationsEnumFactory.java         |   6 +-
 .../AppointmentstatusEnumFactory.java         |   6 +-
 .../AssertDirectionCodesEnumFactory.java      |   6 +-
 .../AssertOperatorCodesEnumFactory.java       |   6 +-
 .../AssertResponseCodeTypesEnumFactory.java   |   6 +-
 .../AuditEventActionEnumFactory.java          |   6 +-
 .../AuditEventOutcomeEnumFactory.java         |   6 +-
 .../AuditEventTypeEnumFactory.java            |   6 +-
 .../AuditSourceTypeEnumFactory.java           |   6 +-
 .../BasicResourceTypeEnumFactory.java         |   6 +-
 .../BenefitCategoryEnumFactory.java           |   6 +-
 .../BenefitNetworkEnumFactory.java            |   6 +-
 .../BenefitSubcategoryEnumFactory.java        |   6 +-
 .../codesystems/BenefitTermEnumFactory.java   |   6 +-
 .../codesystems/BenefitTypeEnumFactory.java   |   6 +-
 .../codesystems/BenefitUnitEnumFactory.java   |   6 +-
 .../BindingStrengthEnumFactory.java           |   6 +-
 .../codesystems/BundleTypeEnumFactory.java    |   6 +-
 .../CardinalityBehaviorEnumFactory.java       |   6 +-
 .../CarePlanActivityCategoryEnumFactory.java  |   6 +-
 .../CarePlanActivityStatusEnumFactory.java    |   6 +-
 .../CarePlanRelationshipEnumFactory.java      |   6 +-
 .../CarePlanStatusEnumFactory.java            |   6 +-
 .../CdsRuleActionTypeEnumFactory.java         |   6 +-
 .../CdsRuleParticipantEnumFactory.java        |   6 +-
 .../CdsRuleTriggerTypeEnumFactory.java        |   6 +-
 .../ChoiceListOrientationEnumFactory.java     |   6 +-
 .../ChromosomeHumanEnumFactory.java           |   6 +-
 .../ClaimExceptionEnumFactory.java            |   6 +-
 .../ClaimModifiersEnumFactory.java            |   6 +-
 .../codesystems/ClaimSubtypeEnumFactory.java  |   6 +-
 .../codesystems/ClaimTypeLinkEnumFactory.java |   6 +-
 .../codesystems/ClaimUseLinkEnumFactory.java  |   6 +-
 .../ClassificationOrContextEnumFactory.java   |   6 +-
 .../ClinicalImpressionStatusEnumFactory.java  |   6 +-
 .../CodesystemContentModeEnumFactory.java     |   6 +-
 ...CommunicationRequestStatusEnumFactory.java |   6 +-
 .../CommunicationStatusEnumFactory.java       |   6 +-
 .../CompartmentTypeEnumFactory.java           |   6 +-
 ...CompositionAttestationModeEnumFactory.java |   6 +-
 .../CompositionStatusEnumFactory.java         |   6 +-
 .../ConceptMapEquivalenceEnumFactory.java     |   6 +-
 .../ConceptPropertyTypeEnumFactory.java       |   6 +-
 .../ConditionCategoryEnumFactory.java         |   6 +-
 .../ConditionClinicalEnumFactory.java         |   6 +-
 .../ConditionStateEnumFactory.java            |   6 +-
 .../ConditionVerStatusEnumFactory.java        |   6 +-
 .../ConditionalDeleteStatusEnumFactory.java   |   6 +-
 .../ConformanceExpectationEnumFactory.java    |   6 +-
 .../ConformanceResourceStatusEnumFactory.java |   6 +-
 .../ConformanceStatementKindEnumFactory.java  |   6 +-
 .../ConstraintSeverityEnumFactory.java        |   6 +-
 .../ContactPointSystemEnumFactory.java        |   6 +-
 .../ContactPointUseEnumFactory.java           |   6 +-
 .../ContactentityTypeEnumFactory.java         |   6 +-
 .../codesystems/ContentTypeEnumFactory.java   |   6 +-
 .../ContractActionEnumFactory.java            |   6 +-
 .../ContractActorroleEnumFactory.java         |   6 +-
 .../ContractSignerTypeEnumFactory.java        |   6 +-
 .../ContractSubtypeEnumFactory.java           |   6 +-
 .../ContractTermSubtypeEnumFactory.java       |   6 +-
 .../ContractTermTypeEnumFactory.java          |   6 +-
 .../codesystems/ContractTypeEnumFactory.java  |   6 +-
 .../CopyNumberEventEnumFactory.java           |   6 +-
 .../CoverageExceptionEnumFactory.java         |   6 +-
 .../CqifCqifTriggerTypeEnumFactory.java       |   6 +-
 .../codesystems/DWebTypeEnumFactory.java      |   6 +-
 .../DataAbsentReasonEnumFactory.java          |   6 +-
 .../codesystems/DataTypesEnumFactory.java     |   6 +-
 .../DataelementStringencyEnumFactory.java     |   6 +-
 .../codesystems/DaysOfWeekEnumFactory.java    |   6 +-
 .../DetectedissueSeverityEnumFactory.java     |   6 +-
 .../codesystems/DeviceActionEnumFactory.java  |   6 +-
 .../DeviceUseRequestPriorityEnumFactory.java  |   6 +-
 .../DeviceUseRequestStatusEnumFactory.java    |   6 +-
 .../codesystems/DevicestatusEnumFactory.java  |   6 +-
 .../DiagnosticOrderPriorityEnumFactory.java   |   6 +-
 .../DiagnosticOrderStatusEnumFactory.java     |   6 +-
 .../DiagnosticReportStatusEnumFactory.java    |   6 +-
 .../DigitalMediaSubtypeEnumFactory.java       |   6 +-
 .../DigitalMediaTypeEnumFactory.java          |   6 +-
 .../codesystems/DocumentModeEnumFactory.java  |   6 +-
 .../DocumentReferenceStatusEnumFactory.java   |   6 +-
 .../DocumentRelationshipTypeEnumFactory.java  |   6 +-
 .../EncounterAdmitSourceEnumFactory.java      |   6 +-
 .../EncounterClassEnumFactory.java            |   6 +-
 .../codesystems/EncounterDietEnumFactory.java |   6 +-
 ...ounterDischargeDispositionEnumFactory.java |   6 +-
 .../EncounterLocationStatusEnumFactory.java   |   6 +-
 .../EncounterParticipantTypeEnumFactory.java  |   6 +-
 .../EncounterPriorityEnumFactory.java         |   6 +-
 ...counterSpecialArrangementsEnumFactory.java |   6 +-
 .../EncounterStateEnumFactory.java            |   6 +-
 .../codesystems/EncounterTypeEnumFactory.java |   6 +-
 .../EndpointStatusEnumFactory.java            |   6 +-
 .../EntformulaAdditiveEnumFactory.java        |   6 +-
 .../EpisodeOfCareStatusEnumFactory.java       |   6 +-
 .../codesystems/ExOnsettypeEnumFactory.java   |   6 +-
 .../codesystems/ExProgramCodeEnumFactory.java |   6 +-
 .../ExtensionContextEnumFactory.java          |   6 +-
 .../FilterOperatorEnumFactory.java            |   6 +-
 .../codesystems/FlagCategoryEnumFactory.java  |   6 +-
 .../codesystems/FlagPriorityEnumFactory.java  |   6 +-
 .../codesystems/FlagStatusEnumFactory.java    |   6 +-
 .../codesystems/FmConditionsEnumFactory.java  |   6 +-
 .../model/codesystems/FormsEnumFactory.java   |   6 +-
 .../codesystems/FundsreserveEnumFactory.java  |   6 +-
 .../GaoEvaluationResultCodeEnumFactory.java   |   6 +-
 .../GoalAcceptanceStatusEnumFactory.java      |   6 +-
 .../codesystems/GoalCategoryEnumFactory.java  |   6 +-
 .../codesystems/GoalPriorityEnumFactory.java  |   6 +-
 .../GoalRelationshipTypeEnumFactory.java      |   6 +-
 .../codesystems/GoalStatusEnumFactory.java    |   6 +-
 .../GoalStatusReasonEnumFactory.java          |   6 +-
 .../codesystems/GroupTypeEnumFactory.java     |   6 +-
 .../GroupingBehaviorEnumFactory.java          |   6 +-
 ...GuidanceResponseActionTypeEnumFactory.java |   6 +-
 .../GuidanceResponseStatusEnumFactory.java    |   6 +-
 .../GuideDependencyTypeEnumFactory.java       |   6 +-
 .../codesystems/GuidePageKindEnumFactory.java |   6 +-
 .../GuideResourcePurposeEnumFactory.java      |   6 +-
 .../codesystems/HistoryStatusEnumFactory.java |   6 +-
 .../HspcAbnIntNumericNomEnumFactory.java      |   6 +-
 .../HspcAddressUseEnumFactory.java            |   6 +-
 .../HspcAdmissionSourceEnumFactory.java       |   6 +-
 ...pcAllergyIntoleranceStatusEnumFactory.java |   6 +-
 ...HspcAllergyIntoleranceTypeEnumFactory.java |   6 +-
 .../HspcArrivalStatusEnumFactory.java         |   6 +-
 .../HspcBodytempmethoddeviceEnumFactory.java  |   6 +-
 .../HspcBpmeasmethoddeviceEnumFactory.java    |   6 +-
 .../HspcClinicalAssertStatusEnumFactory.java  |   6 +-
 .../HspcDeltaFlagNumericNomEnumFactory.java   |   6 +-
 ...HspcDepartureTransportModeEnumFactory.java |   6 +-
 .../HspcFetalestimationmethodEnumFactory.java |   6 +-
 .../HspcLocationConditionEnumFactory.java     |   6 +-
 ...eliveryLocationKeyValueSetEnumFactory.java |   6 +-
 ...iceDeliveryLocationNameUseEnumFactory.java |   6 +-
 ...rvationDataOriginationModeEnumFactory.java |   6 +-
 ...tionHeightMeasMethodDeviceEnumFactory.java |   6 +-
 ...pcObservationHeightPrecondEnumFactory.java |   6 +-
 ...tionWeightMeasMethodDeviceEnumFactory.java |   6 +-
 ...pcObservationWeightPrecondEnumFactory.java |   6 +-
 ...izationOrganizationnameuseEnumFactory.java |   6 +-
 ...ganizationOrganizationtypeEnumFactory.java |   6 +-
 .../HspcPatientAdoptionInfoEnumFactory.java   |   6 +-
 .../HspcPatientPersonNameUseEnumFactory.java  |   6 +-
 .../HspcPatientTelecomSystemEnumFactory.java  |   6 +-
 ...tientVeteranMilitaryStatusEnumFactory.java |   6 +-
 ...nerPracticeAffiliationTypeEnumFactory.java |   6 +-
 .../HspcPractitionerPrivilegeEnumFactory.java |   6 +-
 ...cPractitionerTelecomSystemEnumFactory.java |   6 +-
 .../HspcSpecialArrangementEnumFactory.java    |   6 +-
 .../HspcSubstanceCategoryEnumFactory.java     |   6 +-
 .../HspcTelecomUseEnumFactory.java            |   6 +-
 ...VitalsignassociatedprecondEnumFactory.java |   6 +-
 .../codesystems/HttpVerbEnumFactory.java      |   6 +-
 .../Icd10ProceduresEnumFactory.java           |   6 +-
 .../IdentifierTypeEnumFactory.java            |   6 +-
 .../codesystems/IdentifierUseEnumFactory.java |   6 +-
 .../IdentityAssuranceLevelEnumFactory.java    |   6 +-
 ...ecommendationDateCriterionEnumFactory.java |   6 +-
 ...zationRecommendationStatusEnumFactory.java |   6 +-
 .../codesystems/InterventionEnumFactory.java  |   6 +-
 .../codesystems/IssueSeverityEnumFactory.java |   6 +-
 .../codesystems/IssueTypeEnumFactory.java     |   6 +-
 .../codesystems/ItemTypeEnumFactory.java      |   6 +-
 .../LOINC480020AnswerlistEnumFactory.java     |   6 +-
 .../LOINC480194AnswerlistEnumFactory.java     |   6 +-
 .../LOINC530345AnswerlistEnumFactory.java     |   6 +-
 .../codesystems/LinkTypeEnumFactory.java      |   6 +-
 .../codesystems/LinkageTypeEnumFactory.java   |   6 +-
 .../ListEmptyReasonEnumFactory.java           |   6 +-
 .../ListExampleCodesEnumFactory.java          |   6 +-
 .../codesystems/ListItemFlagEnumFactory.java  |   6 +-
 .../codesystems/ListModeEnumFactory.java      |   6 +-
 .../codesystems/ListOrderEnumFactory.java     |   6 +-
 .../codesystems/ListStatusEnumFactory.java    |   6 +-
 .../codesystems/LocationModeEnumFactory.java  |   6 +-
 .../LocationPhysicalTypeEnumFactory.java      |   6 +-
 .../LocationStatusEnumFactory.java            |   6 +-
 .../MapContextTypeEnumFactory.java            |   6 +-
 .../codesystems/MapInputModeEnumFactory.java  |   6 +-
 .../codesystems/MapListModeEnumFactory.java   |   6 +-
 .../codesystems/MapModelModeEnumFactory.java  |   6 +-
 .../codesystems/MapTransformEnumFactory.java  |   6 +-
 .../codesystems/MaritalStatusEnumFactory.java |   6 +-
 .../codesystems/MatchGradeEnumFactory.java    |   6 +-
 .../MeasureDataUsageEnumFactory.java          |   6 +-
 .../MeasurePopulationEnumFactory.java         |   6 +-
 .../MeasureReportStatusEnumFactory.java       |   6 +-
 .../MeasureReportTypeEnumFactory.java         |   6 +-
 .../MeasureScoringEnumFactory.java            |   6 +-
 .../codesystems/MeasureTypeEnumFactory.java   |   6 +-
 .../MeasurementPrincipleEnumFactory.java      |   6 +-
 .../MedicationAdminStatusEnumFactory.java     |   6 +-
 .../MedicationDispenseStatusEnumFactory.java  |   6 +-
 .../MedicationOrderStatusEnumFactory.java     |   6 +-
 .../MedicationStatementStatusEnumFactory.java |   6 +-
 ...essageConformanceEventModeEnumFactory.java |   6 +-
 .../codesystems/MessageEventsEnumFactory.java |   6 +-
 .../MessageReasonEncounterEnumFactory.java    |   6 +-
 ...essageSignificanceCategoryEnumFactory.java |   6 +-
 .../MessageTransportEnumFactory.java          |   6 +-
 .../MetricCalibrationStateEnumFactory.java    |   6 +-
 .../MetricCalibrationTypeEnumFactory.java     |   6 +-
 .../MetricCategoryEnumFactory.java            |   6 +-
 .../codesystems/MetricColorEnumFactory.java   |   6 +-
 .../MetricOperationalStatusEnumFactory.java   |   6 +-
 .../MissingToothReasonEnumFactory.java        |   6 +-
 .../ModuleMetadataContributorEnumFactory.java |   6 +-
 .../ModuleMetadataFocusTypeEnumFactory.java   |   6 +-
 ...ModuleMetadataResourceTypeEnumFactory.java |   6 +-
 .../ModuleMetadataStatusEnumFactory.java      |   6 +-
 .../ModuleMetadataTypeEnumFactory.java        |   6 +-
 .../model/codesystems/NameUseEnumFactory.java |   6 +-
 ...NamingsystemIdentifierTypeEnumFactory.java |   6 +-
 .../NamingsystemTypeEnumFactory.java          |   6 +-
 .../NarrativeStatusEnumFactory.java           |   6 +-
 ...NehtaGlobalStatementValuesEnumFactory.java |   6 +-
 ...agingExaminationResultStatEnumFactory.java |   6 +-
 ...aCancerPrimaryOrRecurrenceEnumFactory.java |   6 +-
 ...NehtaNehtaCrcOperationTypeEnumFactory.java |   6 +-
 ...NehtaCrcPeritoneumInvasionEnumFactory.java |   6 +-
 ...teriorPeritonealReflectionEnumFactory.java |   6 +-
 .../NehtaNehtaDysplasiaEnumFactory.java       |   6 +-
 .../NehtaNehtaFocalNonFocalEnumFactory.java   |   6 +-
 ...taNehtaInvolvedNotinvolvedEnumFactory.java |   6 +-
 ...edNotinvolvedIndeterminateEnumFactory.java |   6 +-
 ...NehtaInvolvedNotinvolvedNaEnumFactory.java |   6 +-
 .../NehtaNehtaMutatedWildtypeEnumFactory.java |   6 +-
 ...NehtaNewCancerOrRecurrenceEnumFactory.java |   6 +-
 ...NehtaNoneIdentifiedPresentEnumFactory.java |   6 +-
 ...aNehtaNotidentifiedPresentEnumFactory.java |   6 +-
 ...tifiedPresentIndeterminateEnumFactory.java |   6 +-
 ...iedPresentPresentextensiveEnumFactory.java |   6 +-
 .../NehtaNehtaPerforationTypeEnumFactory.java |   6 +-
 .../NehtaNehtaPresentAbsentNsEnumFactory.java |   6 +-
 ...rostateRadMarginPositivityEnumFactory.java |   6 +-
 ...ProstateRadTumourLocationsEnumFactory.java |   6 +-
 ...NehtaProstateRadTumourTypeEnumFactory.java |   6 +-
 ...taNehtaReceivedNotreceivedEnumFactory.java |   6 +-
 ...aNehtaResidualTumourStatusEnumFactory.java |   6 +-
 ...sponseToNeoadjuvantTherapyEnumFactory.java |   6 +-
 .../NehtaNehtaStainTypeEnumFactory.java       |   6 +-
 .../NehtaNehtaUnstableStableEnumFactory.java  |   6 +-
 .../NehtaNehtaYesNoNsEnumFactory.java         |   6 +-
 ...athologyTestResultStatusVaEnumFactory.java |   6 +-
 ...ServiceBookingStatusValuesEnumFactory.java |   6 +-
 .../NehtaTumourStageGroupingEnumFactory.java  |   6 +-
 .../NehtaTumourTypeEnumFactory.java           |   6 +-
 .../codesystems/NetworkTypeEnumFactory.java   |   6 +-
 .../codesystems/NoteTypeEnumFactory.java      |   6 +-
 .../NutritionOrderStatusEnumFactory.java      |   6 +-
 .../ObjectLifecycleEnumFactory.java           |   6 +-
 .../codesystems/ObjectRoleEnumFactory.java    |   6 +-
 .../codesystems/ObjectTypeEnumFactory.java    |   6 +-
 .../ObservationCategoryEnumFactory.java       |   6 +-
 ...servationRelationshiptypesEnumFactory.java |   6 +-
 .../ObservationStatusEnumFactory.java         |   6 +-
 .../OccurrenceCodesEnumFactory.java           |   6 +-
 .../OccurrenceSpanCodesEnumFactory.java       |   6 +-
 .../codesystems/OperationKindEnumFactory.java |   6 +-
 .../OperationOutcomeEnumFactory.java          |   6 +-
 .../OperationParameterTypeEnumFactory.java    |   6 +-
 .../OperationParameterUseEnumFactory.java     |   6 +-
 .../OralProsthodonticMaterialEnumFactory.java |   6 +-
 .../OrderSetItemTypeEnumFactory.java          |   6 +-
 .../OrderSetParticipantEnumFactory.java       |   6 +-
 .../codesystems/OrderStatusEnumFactory.java   |   6 +-
 .../OrganizationTypeEnumFactory.java          |   6 +-
 .../ParticipantrequiredEnumFactory.java       |   6 +-
 .../ParticipantstatusEnumFactory.java         |   6 +-
 .../ParticipationstatusEnumFactory.java       |   6 +-
 ...PatientContactRelationshipEnumFactory.java |   6 +-
 .../PatientMpiMatchEnumFactory.java           |   6 +-
 .../codesystems/PayeetypeEnumFactory.java     |   6 +-
 .../PaymentAdjustmentReasonEnumFactory.java   |   6 +-
 .../codesystems/PaymentStatusEnumFactory.java |   6 +-
 .../codesystems/PaymentTypeEnumFactory.java   |   6 +-
 .../PractitionerRoleEnumFactory.java          |   6 +-
 .../PractitionerSpecialtyEnumFactory.java     |   6 +-
 .../PrecheckBehaviorEnumFactory.java          |   6 +-
 ...ocedureProgressStatusCodesEnumFactory.java |   6 +-
 .../ProcedureRelationshipTypeEnumFactory.java |   6 +-
 .../ProcedureRequestPriorityEnumFactory.java  |   6 +-
 .../ProcedureRequestStatusEnumFactory.java    |   6 +-
 .../ProcedureStatusEnumFactory.java           |   6 +-
 .../ProcessOutcomeEnumFactory.java            |   6 +-
 .../ProcessPriorityEnumFactory.java           |   6 +-
 .../ProfileDestinationTypesEnumFactory.java   |   6 +-
 .../ProfileOriginTypesEnumFactory.java        |   6 +-
 .../PropertyRepresentationEnumFactory.java    |   6 +-
 .../ProtocolStatusEnumFactory.java            |   6 +-
 .../codesystems/ProtocolTypeEnumFactory.java  |   6 +-
 .../ProvenanceAgentRoleEnumFactory.java       |   6 +-
 .../ProvenanceAgentTypeEnumFactory.java       |   6 +-
 .../ProvenanceEntityRoleEnumFactory.java      |   6 +-
 .../ProviderQualificationEnumFactory.java     |   6 +-
 ...QicoreAdverseeventCategoryEnumFactory.java |   6 +-
 .../QicoreAdverseeventTypeEnumFactory.java    |   6 +-
 ...QicoreAppropriatenessScoreEnumFactory.java |   6 +-
 .../QicoreCommunicationMediumEnumFactory.java |   6 +-
 ...QicoreConditionCriticalityEnumFactory.java |   6 +-
 ...iagnosticorderPreconditionEnumFactory.java |   6 +-
 ...oreObservationVerificationEnumFactory.java |   6 +-
 ...corePatientMilitaryServiceEnumFactory.java |   6 +-
 .../QuantityComparatorEnumFactory.java        |   6 +-
 .../QuestionMaxOccursEnumFactory.java         |   6 +-
 ...QuestionnaireAnswersStatusEnumFactory.java |   6 +-
 ...estionnaireDisplayCategoryEnumFactory.java |   6 +-
 .../QuestionnaireItemControlEnumFactory.java  |   6 +-
 .../QuestionnaireStatusEnumFactory.java       |   6 +-
 .../ReactionEventCertaintyEnumFactory.java    |   6 +-
 .../ReactionEventSeverityEnumFactory.java     |   6 +-
 ...ReasonMedicationGivenCodesEnumFactory.java |   6 +-
 ...sonMedicationNotGivenCodesEnumFactory.java |   6 +-
 .../ReferenceVersionRulesEnumFactory.java     |   6 +-
 .../ReferencerangeMeaningEnumFactory.java     |   6 +-
 .../ReferralcategoryEnumFactory.java          |   6 +-
 .../ReferralstatusEnumFactory.java            |   6 +-
 .../RelatedClaimRelationshipEnumFactory.java  |   6 +-
 .../codesystems/RelationshipEnumFactory.java  |   6 +-
 .../RemittanceOutcomeEnumFactory.java         |   6 +-
 .../RequiredBehaviorEnumFactory.java          |   6 +-
 .../ResourceAggregationModeEnumFactory.java   |   6 +-
 .../ResourceSlicingRulesEnumFactory.java      |   6 +-
 .../codesystems/ResourceTypesEnumFactory.java |   6 +-
 .../ResourceValidationModeEnumFactory.java    |   6 +-
 .../codesystems/ResponseCodeEnumFactory.java  |   6 +-
 .../RestfulConformanceModeEnumFactory.java    |   6 +-
 .../RestfulInteractionEnumFactory.java        |   6 +-
 .../RestfulSecurityServiceEnumFactory.java    |   6 +-
 .../RiskProbabilityEnumFactory.java           |   6 +-
 .../model/codesystems/RulesetEnumFactory.java |   6 +-
 .../SearchEntryModeEnumFactory.java           |   6 +-
 .../SearchModifierCodeEnumFactory.java        |   6 +-
 .../SearchParamTypeEnumFactory.java           |   6 +-
 .../SearchXpathUsageEnumFactory.java          |   6 +-
 .../SelectionBehaviorEnumFactory.java         |   6 +-
 .../codesystems/SequenceTypeEnumFactory.java  |   6 +-
 .../ServiceCategoryEnumFactory.java           |   6 +-
 .../ServiceModifiersEnumFactory.java          |   6 +-
 .../ServicePharmacyEnumFactory.java           |   6 +-
 .../codesystems/ServicePlaceEnumFactory.java  |   6 +-
 .../ServiceProductEnumFactory.java            |   6 +-
 ...ServiceProvisionConditionsEnumFactory.java |   6 +-
 .../ServiceReferralMethodEnumFactory.java     |   6 +-
 .../codesystems/ServiceTypeEnumFactory.java   |   6 +-
 .../codesystems/ServiceUsclsEnumFactory.java  |   6 +-
 .../codesystems/SignatureTypeEnumFactory.java |   6 +-
 .../codesystems/SlotstatusEnumFactory.java    |   6 +-
 .../codesystems/SpecialValuesEnumFactory.java |   6 +-
 .../SpecimenStatusEnumFactory.java            |   6 +-
 .../StructureDefinitionKindEnumFactory.java   |   6 +-
 .../SubscriptionChannelTypeEnumFactory.java   |   6 +-
 .../SubscriptionStatusEnumFactory.java        |   6 +-
 .../SubscriptionTagEnumFactory.java           |   6 +-
 .../SubstanceCategoryEnumFactory.java         |   6 +-
 .../SupplydeliveryStatusEnumFactory.java      |   6 +-
 .../SupplydeliveryTypeEnumFactory.java        |   6 +-
 .../SupplyrequestKindEnumFactory.java         |   6 +-
 .../SupplyrequestReasonEnumFactory.java       |   6 +-
 .../SupplyrequestStatusEnumFactory.java       |   6 +-
 .../model/codesystems/SurfaceEnumFactory.java |   6 +-
 .../TaskPerformerTypeEnumFactory.java         |   6 +-
 .../codesystems/TaskPriorityEnumFactory.java  |   6 +-
 .../codesystems/TaskStatusEnumFactory.java    |   6 +-
 .../model/codesystems/TeethEnumFactory.java   |   6 +-
 .../TestscriptOperationCodesEnumFactory.java  |   6 +-
 ...iptProfileDestinationTypesEnumFactory.java |   6 +-
 ...stscriptProfileOriginTypesEnumFactory.java |   6 +-
 .../TimingAbbreviationEnumFactory.java        |   6 +-
 .../model/codesystems/ToothEnumFactory.java   |   6 +-
 .../TransactionModeEnumFactory.java           |   6 +-
 .../codesystems/TriggerTypeEnumFactory.java   |   6 +-
 .../TypeDerivationRuleEnumFactory.java        |   6 +-
 .../model/codesystems/UdiEnumFactory.java     |   6 +-
 .../UnknownContentCodeEnumFactory.java        |   6 +-
 .../codesystems/UslabDoEventEnumFactory.java  |   6 +-
 .../codesystems/UslabObsKindEnumFactory.java  |   6 +-
 ...V3AcknowledgementConditionEnumFactory.java |   6 +-
 ...3AcknowledgementDetailCodeEnumFactory.java |   6 +-
 ...3AcknowledgementDetailTypeEnumFactory.java |   6 +-
 .../V3AcknowledgementTypeEnumFactory.java     |   6 +-
 .../codesystems/V3ActClassEnumFactory.java    |   6 +-
 .../codesystems/V3ActCodeEnumFactory.java     |   6 +-
 .../V3ActExposureLevelCodeEnumFactory.java    |   6 +-
 ...3ActInvoiceElementModifierEnumFactory.java |   6 +-
 .../codesystems/V3ActMoodEnumFactory.java     |   6 +-
 .../codesystems/V3ActPriorityEnumFactory.java |   6 +-
 .../codesystems/V3ActReasonEnumFactory.java   |   6 +-
 ...3ActRelationshipCheckpointEnumFactory.java |   6 +-
 .../V3ActRelationshipJoinEnumFactory.java     |   6 +-
 .../V3ActRelationshipSplitEnumFactory.java    |   6 +-
 .../V3ActRelationshipSubsetEnumFactory.java   |   6 +-
 .../V3ActRelationshipTypeEnumFactory.java     |   6 +-
 .../codesystems/V3ActSiteEnumFactory.java     |   6 +-
 .../codesystems/V3ActStatusEnumFactory.java   |   6 +-
 .../V3ActUSPrivacyLawEnumFactory.java         |   6 +-
 .../V3ActUncertaintyEnumFactory.java          |   6 +-
 .../V3AddressPartTypeEnumFactory.java         |   6 +-
 .../codesystems/V3AddressUseEnumFactory.java  |   6 +-
 .../V3AdministrativeGenderEnumFactory.java    |   6 +-
 ...ndianAlaskaNativeLanguagesEnumFactory.java |   6 +-
 .../V3CalendarCycleEnumFactory.java           |   6 +-
 .../codesystems/V3CalendarEnumFactory.java    |   6 +-
 .../V3CalendarTypeEnumFactory.java            |   6 +-
 .../codesystems/V3CharsetEnumFactory.java     |   6 +-
 .../V3CodingRationaleEnumFactory.java         |   6 +-
 ...3CommunicationFunctionTypeEnumFactory.java |   6 +-
 .../V3CompressionAlgorithmEnumFactory.java    |   6 +-
 .../V3ConfidentialityEnumFactory.java         |   6 +-
 .../V3ContainerCapEnumFactory.java            |   6 +-
 .../V3ContainerSeparatorEnumFactory.java      |   6 +-
 .../V3ContentProcessingModeEnumFactory.java   |   6 +-
 .../V3ContextControlEnumFactory.java          |   6 +-
 .../V3DataOperationEnumFactory.java           |   6 +-
 .../V3DeviceAlertLevelEnumFactory.java        |   6 +-
 .../V3DocumentCompletionEnumFactory.java      |   6 +-
 .../V3DocumentStorageEnumFactory.java         |   6 +-
 .../V3EducationLevelEnumFactory.java          |   6 +-
 .../V3EmployeeJobClassEnumFactory.java        |   6 +-
 ...V3EncounterAdmissionSourceEnumFactory.java |   6 +-
 ...V3EncounterSpecialCourtesyEnumFactory.java |   6 +-
 .../codesystems/V3EntityClassEnumFactory.java |   6 +-
 .../codesystems/V3EntityCodeEnumFactory.java  |   6 +-
 .../V3EntityDeterminerEnumFactory.java        |   6 +-
 .../V3EntityHandlingEnumFactory.java          |   6 +-
 .../V3EntityNamePartQualifierEnumFactory.java |   6 +-
 ...3EntityNamePartQualifierR2EnumFactory.java |   6 +-
 .../V3EntityNamePartTypeEnumFactory.java      |   6 +-
 .../V3EntityNamePartTypeR2EnumFactory.java    |   6 +-
 .../V3EntityNameUseEnumFactory.java           |   6 +-
 .../V3EntityNameUseR2EnumFactory.java         |   6 +-
 .../codesystems/V3EntityRiskEnumFactory.java  |   6 +-
 .../V3EntityStatusEnumFactory.java            |   6 +-
 .../V3EquipmentAlertLevelEnumFactory.java     |   6 +-
 .../codesystems/V3EthnicityEnumFactory.java   |   6 +-
 .../V3ExposureModeEnumFactory.java            |   6 +-
 .../V3GTSAbbreviationEnumFactory.java         |   6 +-
 .../V3GenderStatusEnumFactory.java            |   6 +-
 .../V3HL7UpdateModeEnumFactory.java           |   6 +-
 .../codesystems/V3Hl7RealmEnumFactory.java    |   6 +-
 .../V3Hl7V3ConformanceEnumFactory.java        |   6 +-
 .../V3HtmlLinkTypeEnumFactory.java            |   6 +-
 .../V3IdentifierReliabilityEnumFactory.java   |   6 +-
 .../V3IdentifierScopeEnumFactory.java         |   6 +-
 .../V3IntegrityCheckAlgorithmEnumFactory.java |   6 +-
 .../V3LanguageAbilityModeEnumFactory.java     |   6 +-
 ...LanguageAbilityProficiencyEnumFactory.java |   6 +-
 .../V3LivingArrangementEnumFactory.java       |   6 +-
 .../V3LocalMarkupIgnoreEnumFactory.java       |   6 +-
 .../V3LocalRemoteControlStateEnumFactory.java |   6 +-
 ...ManagedParticipationStatusEnumFactory.java |   6 +-
 .../V3MapRelationshipEnumFactory.java         |   6 +-
 .../V3MaritalStatusEnumFactory.java           |   6 +-
 .../V3MessageWaitingPriorityEnumFactory.java  |   6 +-
 .../V3ModifyIndicatorEnumFactory.java         |   6 +-
 .../codesystems/V3NullFlavorEnumFactory.java  |   6 +-
 ...3ObservationInterpretationEnumFactory.java |   6 +-
 .../V3ObservationMethodEnumFactory.java       |   6 +-
 .../V3ObservationValueEnumFactory.java        |   6 +-
 .../V3OrderableDrugFormEnumFactory.java       |   6 +-
 .../V3ParticipationFunctionEnumFactory.java   |   6 +-
 .../V3ParticipationModeEnumFactory.java       |   6 +-
 .../V3ParticipationSignatureEnumFactory.java  |   6 +-
 .../V3ParticipationTypeEnumFactory.java       |   6 +-
 .../V3PatientImportanceEnumFactory.java       |   6 +-
 .../V3PaymentTermsEnumFactory.java            |   6 +-
 .../V3PersonDisabilityTypeEnumFactory.java    |   6 +-
 ...robabilityDistributionTypeEnumFactory.java |   6 +-
 .../V3ProcessingIDEnumFactory.java            |   6 +-
 .../V3ProcessingModeEnumFactory.java          |   6 +-
 .../V3QueryParameterValueEnumFactory.java     |   6 +-
 .../V3QueryPriorityEnumFactory.java           |   6 +-
 .../V3QueryRequestLimitEnumFactory.java       |   6 +-
 .../V3QueryResponseEnumFactory.java           |   6 +-
 .../V3QueryStatusCodeEnumFactory.java         |   6 +-
 .../model/codesystems/V3RaceEnumFactory.java  |   6 +-
 .../V3RelationalOperatorEnumFactory.java      |   6 +-
 .../V3RelationshipConjunctionEnumFactory.java |   6 +-
 .../V3ReligiousAffiliationEnumFactory.java    |   6 +-
 .../V3ResponseLevelEnumFactory.java           |   6 +-
 .../V3ResponseModalityEnumFactory.java        |   6 +-
 .../V3ResponseModeEnumFactory.java            |   6 +-
 .../codesystems/V3RoleClassEnumFactory.java   |   6 +-
 .../codesystems/V3RoleCodeEnumFactory.java    |   6 +-
 .../V3RoleLinkStatusEnumFactory.java          |   6 +-
 .../V3RoleLinkTypeEnumFactory.java            |   6 +-
 .../codesystems/V3RoleStatusEnumFactory.java  |   6 +-
 .../V3RouteOfAdministrationEnumFactory.java   |   6 +-
 .../codesystems/V3SequencingEnumFactory.java  |   6 +-
 .../codesystems/V3SetOperatorEnumFactory.java |   6 +-
 .../V3SpecimenTypeEnumFactory.java            |   6 +-
 ...SubstanceAdminSubstitutionEnumFactory.java |   6 +-
 .../V3SubstitutionConditionEnumFactory.java   |   6 +-
 ...V3TableCellHorizontalAlignEnumFactory.java |   6 +-
 .../V3TableCellScopeEnumFactory.java          |   6 +-
 .../V3TableCellVerticalAlignEnumFactory.java  |   6 +-
 .../codesystems/V3TableFrameEnumFactory.java  |   6 +-
 .../codesystems/V3TableRulesEnumFactory.java  |   6 +-
 .../V3TargetAwarenessEnumFactory.java         |   6 +-
 ...ecommunicationCapabilitiesEnumFactory.java |   6 +-
 .../codesystems/V3TimingEventEnumFactory.java |   6 +-
 ...issionRelationshipTypeCodeEnumFactory.java |   6 +-
 .../V3TribalEntityUSEnumFactory.java          |   6 +-
 .../V3VaccineManufacturerEnumFactory.java     |   6 +-
 ...cinationProtocolDoseStatusEnumFactory.java |   6 +-
 ...onProtocolDoseStatusReasonEnumFactory.java |   6 +-
 .../codesystems/ValueCodesEnumFactory.java    |   6 +-
 .../codesystems/VariantStateEnumFactory.java  |   6 +-
 .../VersioningPolicyEnumFactory.java          |   6 +-
 .../VisionBaseCodesEnumFactory.java           |   6 +-
 .../VisionEyeCodesEnumFactory.java            |   6 +-
 .../codesystems/VisionProductEnumFactory.java |   6 +-
 .../XdsRelationshipTypeEnumFactory.java       |   6 +-
 631 files changed, 2892 insertions(+), 1446 deletions(-)

diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Account.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Account.java
index 92fa9a25e9..ca92ab2fbb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Account.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Account.java
@@ -152,12 +152,14 @@ public Enumeration<AccountStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AccountStatus code) {
-      if (code == AccountStatus.ACTIVE)
+       if (code == AccountStatus.NULL)
+           return null;
+       if (code == AccountStatus.ACTIVE)
         return "active";
       if (code == AccountStatus.INACTIVE)
         return "inactive";
       return "?";
-    }
+   }
 
     public String toSystem(AccountStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ActionDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ActionDefinition.java
index 99f058429f..2569df318d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ActionDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ActionDefinition.java
@@ -154,12 +154,14 @@ public Enumeration<ActionRelationshipType> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(ActionRelationshipType code) {
-      if (code == ActionRelationshipType.BEFORE)
+       if (code == ActionRelationshipType.NULL)
+           return null;
+       if (code == ActionRelationshipType.BEFORE)
         return "before";
       if (code == ActionRelationshipType.AFTER)
         return "after";
       return "?";
-    }
+   }
 
     public String toSystem(ActionRelationshipType code) {
       return code.getSystem();
@@ -269,12 +271,14 @@ public Enumeration<ActionRelationshipAnchor> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(ActionRelationshipAnchor code) {
-      if (code == ActionRelationshipAnchor.START)
+       if (code == ActionRelationshipAnchor.NULL)
+           return null;
+       if (code == ActionRelationshipAnchor.START)
         return "start";
       if (code == ActionRelationshipAnchor.END)
         return "end";
       return "?";
-    }
+   }
 
     public String toSystem(ActionRelationshipAnchor code) {
       return code.getSystem();
@@ -402,14 +406,16 @@ public Enumeration<ParticipantType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ParticipantType code) {
-      if (code == ParticipantType.PATIENT)
+       if (code == ParticipantType.NULL)
+           return null;
+       if (code == ParticipantType.PATIENT)
         return "patient";
       if (code == ParticipantType.PRACTITIONER)
         return "practitioner";
       if (code == ParticipantType.RELATEDPERSON)
         return "related-person";
       return "?";
-    }
+   }
 
     public String toSystem(ParticipantType code) {
       return code.getSystem();
@@ -555,7 +561,9 @@ public Enumeration<ActionType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ActionType code) {
-      if (code == ActionType.CREATE)
+       if (code == ActionType.NULL)
+           return null;
+       if (code == ActionType.CREATE)
         return "create";
       if (code == ActionType.UPDATE)
         return "update";
@@ -564,7 +572,7 @@ public String toCode(ActionType code) {
       if (code == ActionType.FIREEVENT)
         return "fire-event";
       return "?";
-    }
+   }
 
     public String toSystem(ActionType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Address.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Address.java
index 66f09586d2..65e7099d20 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Address.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Address.java
@@ -192,7 +192,9 @@ public Enumeration<AddressUse> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AddressUse code) {
-      if (code == AddressUse.HOME)
+       if (code == AddressUse.NULL)
+           return null;
+       if (code == AddressUse.HOME)
         return "home";
       if (code == AddressUse.WORK)
         return "work";
@@ -201,7 +203,7 @@ public String toCode(AddressUse code) {
       if (code == AddressUse.OLD)
         return "old";
       return "?";
-    }
+   }
 
     public String toSystem(AddressUse code) {
       return code.getSystem();
@@ -329,14 +331,16 @@ public Enumeration<AddressType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AddressType code) {
-      if (code == AddressType.POSTAL)
+       if (code == AddressType.NULL)
+           return null;
+       if (code == AddressType.POSTAL)
         return "postal";
       if (code == AddressType.PHYSICAL)
         return "physical";
       if (code == AddressType.BOTH)
         return "both";
       return "?";
-    }
+   }
 
     public String toSystem(AddressType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AllergyIntolerance.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AllergyIntolerance.java
index 31fa41e193..545dbf4978 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AllergyIntolerance.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AllergyIntolerance.java
@@ -250,7 +250,9 @@ public Enumeration<AllergyIntoleranceStatus> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(AllergyIntoleranceStatus code) {
-      if (code == AllergyIntoleranceStatus.ACTIVE)
+       if (code == AllergyIntoleranceStatus.NULL)
+           return null;
+       if (code == AllergyIntoleranceStatus.ACTIVE)
         return "active";
       if (code == AllergyIntoleranceStatus.UNCONFIRMED)
         return "unconfirmed";
@@ -265,7 +267,7 @@ public String toCode(AllergyIntoleranceStatus code) {
       if (code == AllergyIntoleranceStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceStatus code) {
       return code.getSystem();
@@ -381,12 +383,14 @@ public Enumeration<AllergyIntoleranceType> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(AllergyIntoleranceType code) {
-      if (code == AllergyIntoleranceType.ALLERGY)
+       if (code == AllergyIntoleranceType.NULL)
+           return null;
+       if (code == AllergyIntoleranceType.ALLERGY)
         return "allergy";
       if (code == AllergyIntoleranceType.INTOLERANCE)
         return "intolerance";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceType code) {
       return code.getSystem();
@@ -532,7 +536,9 @@ public Enumeration<AllergyIntoleranceCategory> fromType(Base code) throws FHIREx
     }
 
     public String toCode(AllergyIntoleranceCategory code) {
-      if (code == AllergyIntoleranceCategory.FOOD)
+       if (code == AllergyIntoleranceCategory.NULL)
+           return null;
+       if (code == AllergyIntoleranceCategory.FOOD)
         return "food";
       if (code == AllergyIntoleranceCategory.MEDICATION)
         return "medication";
@@ -541,7 +547,7 @@ public String toCode(AllergyIntoleranceCategory code) {
       if (code == AllergyIntoleranceCategory.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceCategory code) {
       return code.getSystem();
@@ -671,14 +677,16 @@ public Enumeration<AllergyIntoleranceCriticality> fromType(Base code) throws FHI
     }
 
     public String toCode(AllergyIntoleranceCriticality code) {
-      if (code == AllergyIntoleranceCriticality.LOW)
+       if (code == AllergyIntoleranceCriticality.NULL)
+           return null;
+       if (code == AllergyIntoleranceCriticality.LOW)
         return "low";
       if (code == AllergyIntoleranceCriticality.HIGH)
         return "high";
       if (code == AllergyIntoleranceCriticality.UNABLETOASSESS)
         return "unable-to-assess";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceCriticality code) {
       return code.getSystem();
@@ -810,14 +818,16 @@ public Enumeration<AllergyIntoleranceCertainty> fromType(Base code) throws FHIRE
     }
 
     public String toCode(AllergyIntoleranceCertainty code) {
-      if (code == AllergyIntoleranceCertainty.UNLIKELY)
+       if (code == AllergyIntoleranceCertainty.NULL)
+           return null;
+       if (code == AllergyIntoleranceCertainty.UNLIKELY)
         return "unlikely";
       if (code == AllergyIntoleranceCertainty.LIKELY)
         return "likely";
       if (code == AllergyIntoleranceCertainty.CONFIRMED)
         return "confirmed";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceCertainty code) {
       return code.getSystem();
@@ -945,14 +955,16 @@ public Enumeration<AllergyIntoleranceSeverity> fromType(Base code) throws FHIREx
     }
 
     public String toCode(AllergyIntoleranceSeverity code) {
-      if (code == AllergyIntoleranceSeverity.MILD)
+       if (code == AllergyIntoleranceSeverity.NULL)
+           return null;
+       if (code == AllergyIntoleranceSeverity.MILD)
         return "mild";
       if (code == AllergyIntoleranceSeverity.MODERATE)
         return "moderate";
       if (code == AllergyIntoleranceSeverity.SEVERE)
         return "severe";
       return "?";
-    }
+   }
 
     public String toSystem(AllergyIntoleranceSeverity code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Appointment.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Appointment.java
index a6ca5a65db..e69dccc30d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Appointment.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Appointment.java
@@ -249,7 +249,9 @@ public Enumeration<AppointmentStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AppointmentStatus code) {
-      if (code == AppointmentStatus.PROPOSED)
+       if (code == AppointmentStatus.NULL)
+           return null;
+       if (code == AppointmentStatus.PROPOSED)
         return "proposed";
       if (code == AppointmentStatus.PENDING)
         return "pending";
@@ -264,7 +266,7 @@ public String toCode(AppointmentStatus code) {
       if (code == AppointmentStatus.NOSHOW)
         return "noshow";
       return "?";
-    }
+   }
 
     public String toSystem(AppointmentStatus code) {
       return code.getSystem();
@@ -394,14 +396,16 @@ public Enumeration<ParticipantRequired> fromType(Base code) throws FHIRException
     }
 
     public String toCode(ParticipantRequired code) {
-      if (code == ParticipantRequired.REQUIRED)
+       if (code == ParticipantRequired.NULL)
+           return null;
+       if (code == ParticipantRequired.REQUIRED)
         return "required";
       if (code == ParticipantRequired.OPTIONAL)
         return "optional";
       if (code == ParticipantRequired.INFORMATIONONLY)
         return "information-only";
       return "?";
-    }
+   }
 
     public String toSystem(ParticipantRequired code) {
       return code.getSystem();
@@ -551,7 +555,9 @@ public Enumeration<ParticipationStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(ParticipationStatus code) {
-      if (code == ParticipationStatus.ACCEPTED)
+       if (code == ParticipationStatus.NULL)
+           return null;
+       if (code == ParticipationStatus.ACCEPTED)
         return "accepted";
       if (code == ParticipationStatus.DECLINED)
         return "declined";
@@ -560,7 +566,7 @@ public String toCode(ParticipationStatus code) {
       if (code == ParticipationStatus.NEEDSACTION)
         return "needs-action";
       return "?";
-    }
+   }
 
     public String toSystem(ParticipationStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AuditEvent.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AuditEvent.java
index d9b85909f7..777f0c34b7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AuditEvent.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/AuditEvent.java
@@ -210,7 +210,9 @@ public Enumeration<AuditEventAction> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AuditEventAction code) {
-      if (code == AuditEventAction.C)
+       if (code == AuditEventAction.NULL)
+           return null;
+       if (code == AuditEventAction.C)
         return "C";
       if (code == AuditEventAction.R)
         return "R";
@@ -221,7 +223,7 @@ public String toCode(AuditEventAction code) {
       if (code == AuditEventAction.E)
         return "E";
       return "?";
-    }
+   }
 
     public String toSystem(AuditEventAction code) {
       return code.getSystem();
@@ -370,7 +372,9 @@ public Enumeration<AuditEventOutcome> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AuditEventOutcome code) {
-      if (code == AuditEventOutcome._0)
+       if (code == AuditEventOutcome.NULL)
+           return null;
+       if (code == AuditEventOutcome._0)
         return "0";
       if (code == AuditEventOutcome._4)
         return "4";
@@ -379,7 +383,7 @@ public String toCode(AuditEventOutcome code) {
       if (code == AuditEventOutcome._12)
         return "12";
       return "?";
-    }
+   }
 
     public String toSystem(AuditEventOutcome code) {
       return code.getSystem();
@@ -544,7 +548,9 @@ public Enumeration<AuditEventParticipantNetworkType> fromType(Base code) throws
     }
 
     public String toCode(AuditEventParticipantNetworkType code) {
-      if (code == AuditEventParticipantNetworkType._1)
+       if (code == AuditEventParticipantNetworkType.NULL)
+           return null;
+       if (code == AuditEventParticipantNetworkType._1)
         return "1";
       if (code == AuditEventParticipantNetworkType._2)
         return "2";
@@ -555,7 +561,7 @@ public String toCode(AuditEventParticipantNetworkType code) {
       if (code == AuditEventParticipantNetworkType._5)
         return "5";
       return "?";
-    }
+   }
 
     public String toSystem(AuditEventParticipantNetworkType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Bundle.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Bundle.java
index 8ba653edcf..aa26e72808 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Bundle.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Bundle.java
@@ -288,7 +288,9 @@ public Enumeration<BundleType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(BundleType code) {
-      if (code == BundleType.DOCUMENT)
+       if (code == BundleType.NULL)
+           return null;
+       if (code == BundleType.DOCUMENT)
         return "document";
       if (code == BundleType.MESSAGE)
         return "message";
@@ -307,7 +309,7 @@ public String toCode(BundleType code) {
       if (code == BundleType.COLLECTION)
         return "collection";
       return "?";
-    }
+   }
 
     public String toSystem(BundleType code) {
       return code.getSystem();
@@ -437,14 +439,16 @@ public Enumeration<SearchEntryMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SearchEntryMode code) {
-      if (code == SearchEntryMode.MATCH)
+       if (code == SearchEntryMode.NULL)
+           return null;
+       if (code == SearchEntryMode.MATCH)
         return "match";
       if (code == SearchEntryMode.INCLUDE)
         return "include";
       if (code == SearchEntryMode.OUTCOME)
         return "outcome";
       return "?";
-    }
+   }
 
     public String toSystem(SearchEntryMode code) {
       return code.getSystem();
@@ -590,7 +594,9 @@ public Enumeration<HTTPVerb> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(HTTPVerb code) {
-      if (code == HTTPVerb.GET)
+       if (code == HTTPVerb.NULL)
+           return null;
+       if (code == HTTPVerb.GET)
         return "GET";
       if (code == HTTPVerb.POST)
         return "POST";
@@ -599,7 +605,7 @@ public String toCode(HTTPVerb code) {
       if (code == HTTPVerb.DELETE)
         return "DELETE";
       return "?";
-    }
+   }
 
     public String toSystem(HTTPVerb code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CarePlan.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CarePlan.java
index 775a350c05..b67c5d86fb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CarePlan.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CarePlan.java
@@ -212,7 +212,9 @@ public Enumeration<CarePlanStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(CarePlanStatus code) {
-      if (code == CarePlanStatus.PROPOSED)
+       if (code == CarePlanStatus.NULL)
+           return null;
+       if (code == CarePlanStatus.PROPOSED)
         return "proposed";
       if (code == CarePlanStatus.DRAFT)
         return "draft";
@@ -223,7 +225,7 @@ public String toCode(CarePlanStatus code) {
       if (code == CarePlanStatus.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(CarePlanStatus code) {
       return code.getSystem();
@@ -352,14 +354,16 @@ public Enumeration<CarePlanRelationship> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(CarePlanRelationship code) {
-      if (code == CarePlanRelationship.INCLUDES)
+       if (code == CarePlanRelationship.NULL)
+           return null;
+       if (code == CarePlanRelationship.INCLUDES)
         return "includes";
       if (code == CarePlanRelationship.REPLACES)
         return "replaces";
       if (code == CarePlanRelationship.FULFILLS)
         return "fulfills";
       return "?";
-    }
+   }
 
     public String toSystem(CarePlanRelationship code) {
       return code.getSystem();
@@ -543,7 +547,9 @@ public Enumeration<CarePlanActivityStatus> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(CarePlanActivityStatus code) {
-      if (code == CarePlanActivityStatus.NOTSTARTED)
+       if (code == CarePlanActivityStatus.NULL)
+           return null;
+       if (code == CarePlanActivityStatus.NOTSTARTED)
         return "not-started";
       if (code == CarePlanActivityStatus.SCHEDULED)
         return "scheduled";
@@ -556,7 +562,7 @@ public String toCode(CarePlanActivityStatus code) {
       if (code == CarePlanActivityStatus.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(CarePlanActivityStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Claim.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Claim.java
index 3c7c851b81..7566f87466 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Claim.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Claim.java
@@ -211,7 +211,9 @@ public Enumeration<ClaimType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ClaimType code) {
-      if (code == ClaimType.INSTITUTIONAL)
+       if (code == ClaimType.NULL)
+           return null;
+       if (code == ClaimType.INSTITUTIONAL)
         return "institutional";
       if (code == ClaimType.ORAL)
         return "oral";
@@ -222,7 +224,7 @@ public String toCode(ClaimType code) {
       if (code == ClaimType.VISION)
         return "vision";
       return "?";
-    }
+   }
 
     public String toSystem(ClaimType code) {
       return code.getSystem();
@@ -370,7 +372,9 @@ public Enumeration<Use> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(Use code) {
-      if (code == Use.COMPLETE)
+       if (code == Use.NULL)
+           return null;
+       if (code == Use.COMPLETE)
         return "complete";
       if (code == Use.PROPOSED)
         return "proposed";
@@ -379,7 +383,7 @@ public String toCode(Use code) {
       if (code == Use.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(Use code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ClinicalImpression.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ClinicalImpression.java
index e8b505457a..1f911a904c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ClinicalImpression.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ClinicalImpression.java
@@ -178,14 +178,16 @@ public Enumeration<ClinicalImpressionStatus> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(ClinicalImpressionStatus code) {
-      if (code == ClinicalImpressionStatus.INPROGRESS)
+       if (code == ClinicalImpressionStatus.NULL)
+           return null;
+       if (code == ClinicalImpressionStatus.INPROGRESS)
         return "in-progress";
       if (code == ClinicalImpressionStatus.COMPLETED)
         return "completed";
       if (code == ClinicalImpressionStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(ClinicalImpressionStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CodeSystem.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CodeSystem.java
index 06abb52e57..c85d9a41f9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CodeSystem.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CodeSystem.java
@@ -194,7 +194,9 @@ public Enumeration<CodeSystemContentMode> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(CodeSystemContentMode code) {
-      if (code == CodeSystemContentMode.NOTPRESENT)
+       if (code == CodeSystemContentMode.NULL)
+           return null;
+       if (code == CodeSystemContentMode.NOTPRESENT)
         return "not-present";
       if (code == CodeSystemContentMode.EXAMPLAR)
         return "examplar";
@@ -203,7 +205,7 @@ public String toCode(CodeSystemContentMode code) {
       if (code == CodeSystemContentMode.COMPLETE)
         return "complete";
       return "?";
-    }
+   }
 
     public String toSystem(CodeSystemContentMode code) {
       return code.getSystem();
@@ -388,7 +390,9 @@ public Enumeration<PropertyType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(PropertyType code) {
-      if (code == PropertyType.CODE)
+       if (code == PropertyType.NULL)
+           return null;
+       if (code == PropertyType.CODE)
         return "code";
       if (code == PropertyType.CODING)
         return "Coding";
@@ -401,7 +405,7 @@ public String toCode(PropertyType code) {
       if (code == PropertyType.DATETIME)
         return "dateTime";
       return "?";
-    }
+   }
 
     public String toSystem(PropertyType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Communication.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Communication.java
index 29daff78be..d6ce9e7c6c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Communication.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Communication.java
@@ -210,7 +210,9 @@ public Enumeration<CommunicationStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(CommunicationStatus code) {
-      if (code == CommunicationStatus.INPROGRESS)
+       if (code == CommunicationStatus.NULL)
+           return null;
+       if (code == CommunicationStatus.INPROGRESS)
         return "in-progress";
       if (code == CommunicationStatus.COMPLETED)
         return "completed";
@@ -221,7 +223,7 @@ public String toCode(CommunicationStatus code) {
       if (code == CommunicationStatus.FAILED)
         return "failed";
       return "?";
-    }
+   }
 
     public String toSystem(CommunicationStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CommunicationRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CommunicationRequest.java
index aea7ac9a74..b352badeb6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CommunicationRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CommunicationRequest.java
@@ -301,7 +301,9 @@ public Enumeration<CommunicationRequestStatus> fromType(Base code) throws FHIREx
     }
 
     public String toCode(CommunicationRequestStatus code) {
-      if (code == CommunicationRequestStatus.PROPOSED)
+       if (code == CommunicationRequestStatus.NULL)
+           return null;
+       if (code == CommunicationRequestStatus.PROPOSED)
         return "proposed";
       if (code == CommunicationRequestStatus.PLANNED)
         return "planned";
@@ -322,7 +324,7 @@ public String toCode(CommunicationRequestStatus code) {
       if (code == CommunicationRequestStatus.FAILED)
         return "failed";
       return "?";
-    }
+   }
 
     public String toSystem(CommunicationRequestStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CompartmentDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CompartmentDefinition.java
index 74ae519356..dfa7b9f55d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CompartmentDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/CompartmentDefinition.java
@@ -209,7 +209,9 @@ public Enumeration<CompartmentType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(CompartmentType code) {
-      if (code == CompartmentType.PATIENT)
+       if (code == CompartmentType.NULL)
+           return null;
+       if (code == CompartmentType.PATIENT)
         return "Patient";
       if (code == CompartmentType.ENCOUNTER)
         return "Encounter";
@@ -220,7 +222,7 @@ public String toCode(CompartmentType code) {
       if (code == CompartmentType.DEVICE)
         return "Device";
       return "?";
-    }
+   }
 
     public String toSystem(CompartmentType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Composition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Composition.java
index 006cd55540..d2e31d9af9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Composition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Composition.java
@@ -202,7 +202,9 @@ public Enumeration<CompositionStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(CompositionStatus code) {
-      if (code == CompositionStatus.PRELIMINARY)
+       if (code == CompositionStatus.NULL)
+           return null;
+       if (code == CompositionStatus.PRELIMINARY)
         return "preliminary";
       if (code == CompositionStatus.FINAL)
         return "final";
@@ -211,7 +213,7 @@ public String toCode(CompositionStatus code) {
       if (code == CompositionStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(CompositionStatus code) {
       return code.getSystem();
@@ -359,7 +361,9 @@ public Enumeration<CompositionAttestationMode> fromType(Base code) throws FHIREx
     }
 
     public String toCode(CompositionAttestationMode code) {
-      if (code == CompositionAttestationMode.PERSONAL)
+       if (code == CompositionAttestationMode.NULL)
+           return null;
+       if (code == CompositionAttestationMode.PERSONAL)
         return "personal";
       if (code == CompositionAttestationMode.PROFESSIONAL)
         return "professional";
@@ -368,7 +372,7 @@ public String toCode(CompositionAttestationMode code) {
       if (code == CompositionAttestationMode.OFFICIAL)
         return "official";
       return "?";
-    }
+   }
 
     public String toSystem(CompositionAttestationMode code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Condition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Condition.java
index 712c049668..6db6525938 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Condition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Condition.java
@@ -233,7 +233,9 @@ public Enumeration<ConditionVerificationStatus> fromType(Base code) throws FHIRE
     }
 
     public String toCode(ConditionVerificationStatus code) {
-      if (code == ConditionVerificationStatus.PROVISIONAL)
+       if (code == ConditionVerificationStatus.NULL)
+           return null;
+       if (code == ConditionVerificationStatus.PROVISIONAL)
         return "provisional";
       if (code == ConditionVerificationStatus.DIFFERENTIAL)
         return "differential";
@@ -246,7 +248,7 @@ public String toCode(ConditionVerificationStatus code) {
       if (code == ConditionVerificationStatus.UNKNOWN)
         return "unknown";
       return "?";
-    }
+   }
 
     public String toSystem(ConditionVerificationStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Conformance.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Conformance.java
index 86e8e05063..7adaea573e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Conformance.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Conformance.java
@@ -182,14 +182,16 @@ public Enumeration<ConformanceStatementKind> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(ConformanceStatementKind code) {
-      if (code == ConformanceStatementKind.INSTANCE)
+       if (code == ConformanceStatementKind.NULL)
+           return null;
+       if (code == ConformanceStatementKind.INSTANCE)
         return "instance";
       if (code == ConformanceStatementKind.CAPABILITY)
         return "capability";
       if (code == ConformanceStatementKind.REQUIREMENTS)
         return "requirements";
       return "?";
-    }
+   }
 
     public String toSystem(ConformanceStatementKind code) {
       return code.getSystem();
@@ -335,7 +337,9 @@ public Enumeration<UnknownContentCode> fromType(Base code) throws FHIRException
     }
 
     public String toCode(UnknownContentCode code) {
-      if (code == UnknownContentCode.NO)
+       if (code == UnknownContentCode.NULL)
+           return null;
+       if (code == UnknownContentCode.NO)
         return "no";
       if (code == UnknownContentCode.EXTENSIONS)
         return "extensions";
@@ -344,7 +348,7 @@ public String toCode(UnknownContentCode code) {
       if (code == UnknownContentCode.BOTH)
         return "both";
       return "?";
-    }
+   }
 
     public String toSystem(UnknownContentCode code) {
       return code.getSystem();
@@ -454,12 +458,14 @@ public Enumeration<RestfulConformanceMode> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(RestfulConformanceMode code) {
-      if (code == RestfulConformanceMode.CLIENT)
+       if (code == RestfulConformanceMode.NULL)
+           return null;
+       if (code == RestfulConformanceMode.CLIENT)
         return "client";
       if (code == RestfulConformanceMode.SERVER)
         return "server";
       return "?";
-    }
+   }
 
     public String toSystem(RestfulConformanceMode code) {
       return code.getSystem();
@@ -677,7 +683,9 @@ public Enumeration<TypeRestfulInteraction> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(TypeRestfulInteraction code) {
-      if (code == TypeRestfulInteraction.READ)
+       if (code == TypeRestfulInteraction.NULL)
+           return null;
+       if (code == TypeRestfulInteraction.READ)
         return "read";
       if (code == TypeRestfulInteraction.VREAD)
         return "vread";
@@ -694,7 +702,7 @@ public String toCode(TypeRestfulInteraction code) {
       if (code == TypeRestfulInteraction.SEARCHTYPE)
         return "search-type";
       return "?";
-    }
+   }
 
     public String toSystem(TypeRestfulInteraction code) {
       return code.getSystem();
@@ -823,14 +831,16 @@ public Enumeration<ResourceVersionPolicy> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(ResourceVersionPolicy code) {
-      if (code == ResourceVersionPolicy.NOVERSION)
+       if (code == ResourceVersionPolicy.NULL)
+           return null;
+       if (code == ResourceVersionPolicy.NOVERSION)
         return "no-version";
       if (code == ResourceVersionPolicy.VERSIONED)
         return "versioned";
       if (code == ResourceVersionPolicy.VERSIONEDUPDATE)
         return "versioned-update";
       return "?";
-    }
+   }
 
     public String toSystem(ResourceVersionPolicy code) {
       return code.getSystem();
@@ -959,14 +969,16 @@ public Enumeration<ConditionalDeleteStatus> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(ConditionalDeleteStatus code) {
-      if (code == ConditionalDeleteStatus.NOTSUPPORTED)
+       if (code == ConditionalDeleteStatus.NULL)
+           return null;
+       if (code == ConditionalDeleteStatus.NOTSUPPORTED)
         return "not-supported";
       if (code == ConditionalDeleteStatus.SINGLE)
         return "single";
       if (code == ConditionalDeleteStatus.MULTIPLE)
         return "multiple";
       return "?";
-    }
+   }
 
     public String toSystem(ConditionalDeleteStatus code) {
       return code.getSystem();
@@ -1231,7 +1243,9 @@ public Enumeration<SearchModifierCode> fromType(Base code) throws FHIRException
     }
 
     public String toCode(SearchModifierCode code) {
-      if (code == SearchModifierCode.MISSING)
+       if (code == SearchModifierCode.NULL)
+           return null;
+       if (code == SearchModifierCode.MISSING)
         return "missing";
       if (code == SearchModifierCode.EXACT)
         return "exact";
@@ -1252,7 +1266,7 @@ public String toCode(SearchModifierCode code) {
       if (code == SearchModifierCode.TYPE)
         return "type";
       return "?";
-    }
+   }
 
     public String toSystem(SearchModifierCode code) {
       return code.getSystem();
@@ -1380,14 +1394,16 @@ public Enumeration<SystemRestfulInteraction> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(SystemRestfulInteraction code) {
-      if (code == SystemRestfulInteraction.TRANSACTION)
+       if (code == SystemRestfulInteraction.NULL)
+           return null;
+       if (code == SystemRestfulInteraction.TRANSACTION)
         return "transaction";
       if (code == SystemRestfulInteraction.SEARCHSYSTEM)
         return "search-system";
       if (code == SystemRestfulInteraction.HISTORYSYSTEM)
         return "history-system";
       return "?";
-    }
+   }
 
     public String toSystem(SystemRestfulInteraction code) {
       return code.getSystem();
@@ -1533,7 +1549,9 @@ public Enumeration<TransactionMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(TransactionMode code) {
-      if (code == TransactionMode.NOTSUPPORTED)
+       if (code == TransactionMode.NULL)
+           return null;
+       if (code == TransactionMode.NOTSUPPORTED)
         return "not-supported";
       if (code == TransactionMode.BATCH)
         return "batch";
@@ -1542,7 +1560,7 @@ public String toCode(TransactionMode code) {
       if (code == TransactionMode.BOTH)
         return "both";
       return "?";
-    }
+   }
 
     public String toSystem(TransactionMode code) {
       return code.getSystem();
@@ -1674,14 +1692,16 @@ public Enumeration<MessageSignificanceCategory> fromType(Base code) throws FHIRE
     }
 
     public String toCode(MessageSignificanceCategory code) {
-      if (code == MessageSignificanceCategory.CONSEQUENCE)
+       if (code == MessageSignificanceCategory.NULL)
+           return null;
+       if (code == MessageSignificanceCategory.CONSEQUENCE)
         return "Consequence";
       if (code == MessageSignificanceCategory.CURRENCY)
         return "Currency";
       if (code == MessageSignificanceCategory.NOTIFICATION)
         return "Notification";
       return "?";
-    }
+   }
 
     public String toSystem(MessageSignificanceCategory code) {
       return code.getSystem();
@@ -1791,12 +1811,14 @@ public Enumeration<ConformanceEventMode> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(ConformanceEventMode code) {
-      if (code == ConformanceEventMode.SENDER)
+       if (code == ConformanceEventMode.NULL)
+           return null;
+       if (code == ConformanceEventMode.SENDER)
         return "sender";
       if (code == ConformanceEventMode.RECEIVER)
         return "receiver";
       return "?";
-    }
+   }
 
     public String toSystem(ConformanceEventMode code) {
       return code.getSystem();
@@ -1906,12 +1928,14 @@ public Enumeration<DocumentMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DocumentMode code) {
-      if (code == DocumentMode.PRODUCER)
+       if (code == DocumentMode.NULL)
+           return null;
+       if (code == DocumentMode.PRODUCER)
         return "producer";
       if (code == DocumentMode.CONSUMER)
         return "consumer";
       return "?";
-    }
+   }
 
     public String toSystem(DocumentMode code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ContactPoint.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ContactPoint.java
index ebe3089d75..8b26ef38a9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ContactPoint.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ContactPoint.java
@@ -211,7 +211,9 @@ public Enumeration<ContactPointSystem> fromType(Base code) throws FHIRException
     }
 
     public String toCode(ContactPointSystem code) {
-      if (code == ContactPointSystem.PHONE)
+       if (code == ContactPointSystem.NULL)
+           return null;
+       if (code == ContactPointSystem.PHONE)
         return "phone";
       if (code == ContactPointSystem.FAX)
         return "fax";
@@ -222,7 +224,7 @@ public String toCode(ContactPointSystem code) {
       if (code == ContactPointSystem.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(ContactPointSystem code) {
       return code.getSystem();
@@ -393,7 +395,9 @@ public Enumeration<ContactPointUse> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ContactPointUse code) {
-      if (code == ContactPointUse.HOME)
+       if (code == ContactPointUse.NULL)
+           return null;
+       if (code == ContactPointUse.HOME)
         return "home";
       if (code == ContactPointUse.WORK)
         return "work";
@@ -404,7 +408,7 @@ public String toCode(ContactPointUse code) {
       if (code == ContactPointUse.MOBILE)
         return "mobile";
       return "?";
-    }
+   }
 
     public String toSystem(ContactPointUse code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DataElement.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DataElement.java
index 5e8a085a15..13e8310b4a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DataElement.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DataElement.java
@@ -240,7 +240,9 @@ public Enumeration<DataElementStringency> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(DataElementStringency code) {
-      if (code == DataElementStringency.COMPARABLE)
+       if (code == DataElementStringency.NULL)
+           return null;
+       if (code == DataElementStringency.COMPARABLE)
         return "comparable";
       if (code == DataElementStringency.FULLYSPECIFIED)
         return "fully-specified";
@@ -253,7 +255,7 @@ public String toCode(DataElementStringency code) {
       if (code == DataElementStringency.FLEXIBLE)
         return "flexible";
       return "?";
-    }
+   }
 
     public String toSystem(DataElementStringency code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DetectedIssue.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DetectedIssue.java
index c546ad6ee1..7d5275e951 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DetectedIssue.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DetectedIssue.java
@@ -177,14 +177,16 @@ public Enumeration<DetectedIssueSeverity> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(DetectedIssueSeverity code) {
-      if (code == DetectedIssueSeverity.HIGH)
+       if (code == DetectedIssueSeverity.NULL)
+           return null;
+       if (code == DetectedIssueSeverity.HIGH)
         return "high";
       if (code == DetectedIssueSeverity.MODERATE)
         return "moderate";
       if (code == DetectedIssueSeverity.LOW)
         return "low";
       return "?";
-    }
+   }
 
     public String toSystem(DetectedIssueSeverity code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Device.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Device.java
index 3e2921969e..968be62c98 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Device.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Device.java
@@ -175,14 +175,16 @@ public Enumeration<DeviceStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DeviceStatus code) {
-      if (code == DeviceStatus.AVAILABLE)
+       if (code == DeviceStatus.NULL)
+           return null;
+       if (code == DeviceStatus.AVAILABLE)
         return "available";
       if (code == DeviceStatus.NOTAVAILABLE)
         return "not-available";
       if (code == DeviceStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceComponent.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceComponent.java
index e93f3a8bf4..55dcf2f71d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceComponent.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceComponent.java
@@ -316,7 +316,9 @@ public Enumeration<MeasmntPrinciple> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MeasmntPrinciple code) {
-      if (code == MeasmntPrinciple.OTHER)
+       if (code == MeasmntPrinciple.NULL)
+           return null;
+       if (code == MeasmntPrinciple.OTHER)
         return "other";
       if (code == MeasmntPrinciple.CHEMICAL)
         return "chemical";
@@ -339,7 +341,7 @@ public String toCode(MeasmntPrinciple code) {
       if (code == MeasmntPrinciple.MANUAL)
         return "manual";
       return "?";
-    }
+   }
 
     public String toSystem(MeasmntPrinciple code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceMetric.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceMetric.java
index 7e73972d3b..f4fef4eb92 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceMetric.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceMetric.java
@@ -171,14 +171,16 @@ public Enumeration<DeviceMetricOperationalStatus> fromType(Base code) throws FHI
     }
 
     public String toCode(DeviceMetricOperationalStatus code) {
-      if (code == DeviceMetricOperationalStatus.ON)
+       if (code == DeviceMetricOperationalStatus.NULL)
+           return null;
+       if (code == DeviceMetricOperationalStatus.ON)
         return "on";
       if (code == DeviceMetricOperationalStatus.OFF)
         return "off";
       if (code == DeviceMetricOperationalStatus.STANDBY)
         return "standby";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceMetricOperationalStatus code) {
       return code.getSystem();
@@ -396,7 +398,9 @@ public Enumeration<DeviceMetricColor> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DeviceMetricColor code) {
-      if (code == DeviceMetricColor.BLACK)
+       if (code == DeviceMetricColor.NULL)
+           return null;
+       if (code == DeviceMetricColor.BLACK)
         return "black";
       if (code == DeviceMetricColor.RED)
         return "red";
@@ -413,7 +417,7 @@ public String toCode(DeviceMetricColor code) {
       if (code == DeviceMetricColor.WHITE)
         return "white";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceMetricColor code) {
       return code.getSystem();
@@ -560,7 +564,9 @@ public Enumeration<DeviceMetricCategory> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(DeviceMetricCategory code) {
-      if (code == DeviceMetricCategory.MEASUREMENT)
+       if (code == DeviceMetricCategory.NULL)
+           return null;
+       if (code == DeviceMetricCategory.MEASUREMENT)
         return "measurement";
       if (code == DeviceMetricCategory.SETTING)
         return "setting";
@@ -569,7 +575,7 @@ public String toCode(DeviceMetricCategory code) {
       if (code == DeviceMetricCategory.UNSPECIFIED)
         return "unspecified";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceMetricCategory code) {
       return code.getSystem();
@@ -715,7 +721,9 @@ public Enumeration<DeviceMetricCalibrationType> fromType(Base code) throws FHIRE
     }
 
     public String toCode(DeviceMetricCalibrationType code) {
-      if (code == DeviceMetricCalibrationType.UNSPECIFIED)
+       if (code == DeviceMetricCalibrationType.NULL)
+           return null;
+       if (code == DeviceMetricCalibrationType.UNSPECIFIED)
         return "unspecified";
       if (code == DeviceMetricCalibrationType.OFFSET)
         return "offset";
@@ -724,7 +732,7 @@ public String toCode(DeviceMetricCalibrationType code) {
       if (code == DeviceMetricCalibrationType.TWOPOINT)
         return "two-point";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceMetricCalibrationType code) {
       return code.getSystem();
@@ -870,7 +878,9 @@ public Enumeration<DeviceMetricCalibrationState> fromType(Base code) throws FHIR
     }
 
     public String toCode(DeviceMetricCalibrationState code) {
-      if (code == DeviceMetricCalibrationState.NOTCALIBRATED)
+       if (code == DeviceMetricCalibrationState.NULL)
+           return null;
+       if (code == DeviceMetricCalibrationState.NOTCALIBRATED)
         return "not-calibrated";
       if (code == DeviceMetricCalibrationState.CALIBRATIONREQUIRED)
         return "calibration-required";
@@ -879,7 +889,7 @@ public String toCode(DeviceMetricCalibrationState code) {
       if (code == DeviceMetricCalibrationState.UNSPECIFIED)
         return "unspecified";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceMetricCalibrationState code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceUseRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceUseRequest.java
index 76793efaf8..2ff2f961d1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceUseRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DeviceUseRequest.java
@@ -298,7 +298,9 @@ public Enumeration<DeviceUseRequestStatus> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(DeviceUseRequestStatus code) {
-      if (code == DeviceUseRequestStatus.PROPOSED)
+       if (code == DeviceUseRequestStatus.NULL)
+           return null;
+       if (code == DeviceUseRequestStatus.PROPOSED)
         return "proposed";
       if (code == DeviceUseRequestStatus.PLANNED)
         return "planned";
@@ -319,7 +321,7 @@ public String toCode(DeviceUseRequestStatus code) {
       if (code == DeviceUseRequestStatus.ABORTED)
         return "aborted";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceUseRequestStatus code) {
       return code.getSystem();
@@ -465,7 +467,9 @@ public Enumeration<DeviceUseRequestPriority> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(DeviceUseRequestPriority code) {
-      if (code == DeviceUseRequestPriority.ROUTINE)
+       if (code == DeviceUseRequestPriority.NULL)
+           return null;
+       if (code == DeviceUseRequestPriority.ROUTINE)
         return "routine";
       if (code == DeviceUseRequestPriority.URGENT)
         return "urgent";
@@ -474,7 +478,7 @@ public String toCode(DeviceUseRequestPriority code) {
       if (code == DeviceUseRequestPriority.ASAP)
         return "asap";
       return "?";
-    }
+   }
 
     public String toSystem(DeviceUseRequestPriority code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticOrder.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticOrder.java
index d343e1235f..1de28592dc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticOrder.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticOrder.java
@@ -371,7 +371,9 @@ public Enumeration<DiagnosticOrderStatus> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(DiagnosticOrderStatus code) {
-      if (code == DiagnosticOrderStatus.PROPOSED)
+       if (code == DiagnosticOrderStatus.NULL)
+           return null;
+       if (code == DiagnosticOrderStatus.PROPOSED)
         return "proposed";
       if (code == DiagnosticOrderStatus.DRAFT)
         return "draft";
@@ -400,7 +402,7 @@ public String toCode(DiagnosticOrderStatus code) {
       if (code == DiagnosticOrderStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(DiagnosticOrderStatus code) {
       return code.getSystem();
@@ -546,7 +548,9 @@ public Enumeration<DiagnosticOrderPriority> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(DiagnosticOrderPriority code) {
-      if (code == DiagnosticOrderPriority.ROUTINE)
+       if (code == DiagnosticOrderPriority.NULL)
+           return null;
+       if (code == DiagnosticOrderPriority.ROUTINE)
         return "routine";
       if (code == DiagnosticOrderPriority.URGENT)
         return "urgent";
@@ -555,7 +559,7 @@ public String toCode(DiagnosticOrderPriority code) {
       if (code == DiagnosticOrderPriority.ASAP)
         return "asap";
       return "?";
-    }
+   }
 
     public String toSystem(DiagnosticOrderPriority code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticReport.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticReport.java
index 5898282ea9..4282fbbb79 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticReport.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DiagnosticReport.java
@@ -253,7 +253,9 @@ public Enumeration<DiagnosticReportStatus> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(DiagnosticReportStatus code) {
-      if (code == DiagnosticReportStatus.REGISTERED)
+       if (code == DiagnosticReportStatus.NULL)
+           return null;
+       if (code == DiagnosticReportStatus.REGISTERED)
         return "registered";
       if (code == DiagnosticReportStatus.PARTIAL)
         return "partial";
@@ -268,7 +270,7 @@ public String toCode(DiagnosticReportStatus code) {
       if (code == DiagnosticReportStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(DiagnosticReportStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DocumentReference.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DocumentReference.java
index 762747d165..3369b341ad 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DocumentReference.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/DocumentReference.java
@@ -192,7 +192,9 @@ public Enumeration<DocumentRelationshipType> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(DocumentRelationshipType code) {
-      if (code == DocumentRelationshipType.REPLACES)
+       if (code == DocumentRelationshipType.NULL)
+           return null;
+       if (code == DocumentRelationshipType.REPLACES)
         return "replaces";
       if (code == DocumentRelationshipType.TRANSFORMS)
         return "transforms";
@@ -201,7 +203,7 @@ public String toCode(DocumentRelationshipType code) {
       if (code == DocumentRelationshipType.APPENDS)
         return "appends";
       return "?";
-    }
+   }
 
     public String toSystem(DocumentRelationshipType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ElementDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ElementDefinition.java
index 3d30b8d9b3..f7ba63dfdc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ElementDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ElementDefinition.java
@@ -191,7 +191,9 @@ public Enumeration<PropertyRepresentation> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(PropertyRepresentation code) {
-      if (code == PropertyRepresentation.XMLATTR)
+       if (code == PropertyRepresentation.NULL)
+           return null;
+       if (code == PropertyRepresentation.XMLATTR)
         return "xmlAttr";
       if (code == PropertyRepresentation.XMLTEXT)
         return "xmlText";
@@ -200,7 +202,7 @@ public String toCode(PropertyRepresentation code) {
       if (code == PropertyRepresentation.CDATEXT)
         return "cdaText";
       return "?";
-    }
+   }
 
     public String toSystem(PropertyRepresentation code) {
       return code.getSystem();
@@ -331,14 +333,16 @@ public Enumeration<SlicingRules> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SlicingRules code) {
-      if (code == SlicingRules.CLOSED)
+       if (code == SlicingRules.NULL)
+           return null;
+       if (code == SlicingRules.CLOSED)
         return "closed";
       if (code == SlicingRules.OPEN)
         return "open";
       if (code == SlicingRules.OPENATEND)
         return "openAtEnd";
       return "?";
-    }
+   }
 
     public String toSystem(SlicingRules code) {
       return code.getSystem();
@@ -468,14 +472,16 @@ public Enumeration<AggregationMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AggregationMode code) {
-      if (code == AggregationMode.CONTAINED)
+       if (code == AggregationMode.NULL)
+           return null;
+       if (code == AggregationMode.CONTAINED)
         return "contained";
       if (code == AggregationMode.REFERENCED)
         return "referenced";
       if (code == AggregationMode.BUNDLED)
         return "bundled";
       return "?";
-    }
+   }
 
     public String toSystem(AggregationMode code) {
       return code.getSystem();
@@ -603,14 +609,16 @@ public Enumeration<ReferenceVersionRules> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(ReferenceVersionRules code) {
-      if (code == ReferenceVersionRules.EITHER)
+       if (code == ReferenceVersionRules.NULL)
+           return null;
+       if (code == ReferenceVersionRules.EITHER)
         return "either";
       if (code == ReferenceVersionRules.INDEPENDENT)
         return "independent";
       if (code == ReferenceVersionRules.SPECIFIC)
         return "specific";
       return "?";
-    }
+   }
 
     public String toSystem(ReferenceVersionRules code) {
       return code.getSystem();
@@ -721,12 +729,14 @@ public Enumeration<ConstraintSeverity> fromType(Base code) throws FHIRException
     }
 
     public String toCode(ConstraintSeverity code) {
-      if (code == ConstraintSeverity.ERROR)
+       if (code == ConstraintSeverity.NULL)
+           return null;
+       if (code == ConstraintSeverity.ERROR)
         return "error";
       if (code == ConstraintSeverity.WARNING)
         return "warning";
       return "?";
-    }
+   }
 
     public String toSystem(ConstraintSeverity code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Encounter.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Encounter.java
index 81bfc8b414..2afdcd8a5b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Encounter.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Encounter.java
@@ -227,7 +227,9 @@ public Enumeration<EncounterState> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(EncounterState code) {
-      if (code == EncounterState.PLANNED)
+       if (code == EncounterState.NULL)
+           return null;
+       if (code == EncounterState.PLANNED)
         return "planned";
       if (code == EncounterState.ARRIVED)
         return "arrived";
@@ -240,7 +242,7 @@ public String toCode(EncounterState code) {
       if (code == EncounterState.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(EncounterState code) {
       return code.getSystem();
@@ -482,7 +484,9 @@ public Enumeration<EncounterClass> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(EncounterClass code) {
-      if (code == EncounterClass.INPATIENT)
+       if (code == EncounterClass.NULL)
+           return null;
+       if (code == EncounterClass.INPATIENT)
         return "inpatient";
       if (code == EncounterClass.OUTPATIENT)
         return "outpatient";
@@ -501,7 +505,7 @@ public String toCode(EncounterClass code) {
       if (code == EncounterClass.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(EncounterClass code) {
       return code.getSystem();
@@ -654,7 +658,9 @@ public Enumeration<EncounterLocationStatus> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(EncounterLocationStatus code) {
-      if (code == EncounterLocationStatus.PLANNED)
+       if (code == EncounterLocationStatus.NULL)
+           return null;
+       if (code == EncounterLocationStatus.PLANNED)
         return "planned";
       if (code == EncounterLocationStatus.ACTIVE)
         return "active";
@@ -663,7 +669,7 @@ public String toCode(EncounterLocationStatus code) {
       if (code == EncounterLocationStatus.COMPLETED)
         return "completed";
       return "?";
-    }
+   }
 
     public String toSystem(EncounterLocationStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Enumerations.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Enumerations.java
index 4a0655fb3d..670b0d4078 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Enumerations.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Enumerations.java
@@ -155,12 +155,14 @@ public Enumeration<AbstractType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AbstractType code) {
-      if (code == AbstractType.TYPE)
+       if (code == AbstractType.NULL)
+           return null;
+       if (code == AbstractType.TYPE)
         return "Type";
       if (code == AbstractType.ANY)
         return "Any";
       return "?";
-    }
+   }
 
     public String toSystem(AbstractType code) {
       return code.getSystem();
@@ -306,7 +308,9 @@ public Enumeration<AdministrativeGender> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(AdministrativeGender code) {
-      if (code == AdministrativeGender.MALE)
+       if (code == AdministrativeGender.NULL)
+           return null;
+       if (code == AdministrativeGender.MALE)
         return "male";
       if (code == AdministrativeGender.FEMALE)
         return "female";
@@ -315,7 +319,7 @@ public String toCode(AdministrativeGender code) {
       if (code == AdministrativeGender.UNKNOWN)
         return "unknown";
       return "?";
-    }
+   }
 
     public String toSystem(AdministrativeGender code) {
       return code.getSystem();
@@ -497,7 +501,9 @@ public Enumeration<AgeUnits> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(AgeUnits code) {
-      if (code == AgeUnits.MIN)
+       if (code == AgeUnits.NULL)
+           return null;
+       if (code == AgeUnits.MIN)
         return "min";
       if (code == AgeUnits.H)
         return "h";
@@ -510,7 +516,7 @@ public String toCode(AgeUnits code) {
       if (code == AgeUnits.A)
         return "a";
       return "?";
-    }
+   }
 
     public String toSystem(AgeUnits code) {
       return code.getSystem();
@@ -665,7 +671,9 @@ public Enumeration<BindingStrength> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(BindingStrength code) {
-      if (code == BindingStrength.REQUIRED)
+       if (code == BindingStrength.NULL)
+           return null;
+       if (code == BindingStrength.REQUIRED)
         return "required";
       if (code == BindingStrength.EXTENSIBLE)
         return "extensible";
@@ -674,7 +682,7 @@ public String toCode(BindingStrength code) {
       if (code == BindingStrength.EXAMPLE)
         return "example";
       return "?";
-    }
+   }
 
     public String toSystem(BindingStrength code) {
       return code.getSystem();
@@ -925,7 +933,9 @@ public Enumeration<ConceptMapEquivalence> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(ConceptMapEquivalence code) {
-      if (code == ConceptMapEquivalence.EQUIVALENT)
+       if (code == ConceptMapEquivalence.NULL)
+           return null;
+       if (code == ConceptMapEquivalence.EQUIVALENT)
         return "equivalent";
       if (code == ConceptMapEquivalence.EQUAL)
         return "equal";
@@ -944,7 +954,7 @@ public String toCode(ConceptMapEquivalence code) {
       if (code == ConceptMapEquivalence.DISJOINT)
         return "disjoint";
       return "?";
-    }
+   }
 
     public String toSystem(ConceptMapEquivalence code) {
       return code.getSystem();
@@ -1072,14 +1082,16 @@ public Enumeration<ConformanceResourceStatus> fromType(Base code) throws FHIRExc
     }
 
     public String toCode(ConformanceResourceStatus code) {
-      if (code == ConformanceResourceStatus.DRAFT)
+       if (code == ConformanceResourceStatus.NULL)
+           return null;
+       if (code == ConformanceResourceStatus.DRAFT)
         return "draft";
       if (code == ConformanceResourceStatus.ACTIVE)
         return "active";
       if (code == ConformanceResourceStatus.RETIRED)
         return "retired";
       return "?";
-    }
+   }
 
     public String toSystem(ConformanceResourceStatus code) {
       return code.getSystem();
@@ -1318,7 +1330,9 @@ public Enumeration<DataAbsentReason> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DataAbsentReason code) {
-      if (code == DataAbsentReason.UNKNOWN)
+       if (code == DataAbsentReason.NULL)
+           return null;
+       if (code == DataAbsentReason.UNKNOWN)
         return "unknown";
       if (code == DataAbsentReason.ASKED)
         return "asked";
@@ -1337,7 +1351,7 @@ public String toCode(DataAbsentReason code) {
       if (code == DataAbsentReason.NAN)
         return "NaN";
       return "?";
-    }
+   }
 
     public String toSystem(DataAbsentReason code) {
       return code.getSystem();
@@ -2370,7 +2384,9 @@ public Enumeration<DataType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DataType code) {
-      if (code == DataType.ACTIONDEFINITION)
+       if (code == DataType.NULL)
+           return null;
+       if (code == DataType.ACTIONDEFINITION)
         return "ActionDefinition";
       if (code == DataType.ADDRESS)
         return "Address";
@@ -2473,7 +2489,7 @@ public String toCode(DataType code) {
       if (code == DataType.XHTML)
         return "xhtml";
       return "?";
-    }
+   }
 
     public String toSystem(DataType code) {
       return code.getSystem();
@@ -2601,14 +2617,16 @@ public Enumeration<DocumentReferenceStatus> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(DocumentReferenceStatus code) {
-      if (code == DocumentReferenceStatus.CURRENT)
+       if (code == DocumentReferenceStatus.NULL)
+           return null;
+       if (code == DocumentReferenceStatus.CURRENT)
         return "current";
       if (code == DocumentReferenceStatus.SUPERSEDED)
         return "superseded";
       if (code == DocumentReferenceStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(DocumentReferenceStatus code) {
       return code.getSystem();
@@ -5957,7 +5975,9 @@ public Enumeration<FHIRAllTypes> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(FHIRAllTypes code) {
-      if (code == FHIRAllTypes.ACTIONDEFINITION)
+       if (code == FHIRAllTypes.NULL)
+           return null;
+       if (code == FHIRAllTypes.ACTIONDEFINITION)
         return "ActionDefinition";
       if (code == FHIRAllTypes.ADDRESS)
         return "Address";
@@ -6294,7 +6314,7 @@ public String toCode(FHIRAllTypes code) {
       if (code == FHIRAllTypes.ANY)
         return "Any";
       return "?";
-    }
+   }
 
     public String toSystem(FHIRAllTypes code) {
       return code.getSystem();
@@ -9607,7 +9627,9 @@ public Enumeration<FHIRDefinedType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(FHIRDefinedType code) {
-      if (code == FHIRDefinedType.ACTIONDEFINITION)
+       if (code == FHIRDefinedType.NULL)
+           return null;
+       if (code == FHIRDefinedType.ACTIONDEFINITION)
         return "ActionDefinition";
       if (code == FHIRDefinedType.ADDRESS)
         return "Address";
@@ -9940,7 +9962,7 @@ public String toCode(FHIRDefinedType code) {
       if (code == FHIRDefinedType.VISIONPRESCRIPTION)
         return "VisionPrescription";
       return "?";
-    }
+   }
 
     public String toSystem(FHIRDefinedType code) {
       return code.getSystem();
@@ -10222,7 +10244,9 @@ public Enumeration<MessageEvent> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MessageEvent code) {
-      if (code == MessageEvent.CODESYSTEMEXPAND)
+       if (code == MessageEvent.NULL)
+           return null;
+       if (code == MessageEvent.CODESYSTEMEXPAND)
         return "CodeSystem-expand";
       if (code == MessageEvent.MEDICATIONADMINISTRATIONCOMPLETE)
         return "MedicationAdministration-Complete";
@@ -10245,7 +10269,7 @@ public String toCode(MessageEvent code) {
       if (code == MessageEvent.VALUESETEXPAND)
         return "valueset-expand";
       return "?";
-    }
+   }
 
     public String toSystem(MessageEvent code) {
       return code.getSystem();
@@ -10373,14 +10397,16 @@ public Enumeration<NoteType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(NoteType code) {
-      if (code == NoteType.DISPLAY)
+       if (code == NoteType.NULL)
+           return null;
+       if (code == NoteType.DISPLAY)
         return "display";
       if (code == NoteType.PRINT)
         return "print";
       if (code == NoteType.PRINTOPER)
         return "printoper";
       return "?";
-    }
+   }
 
     public String toSystem(NoteType code) {
       return code.getSystem();
@@ -10490,12 +10516,14 @@ public Enumeration<RemittanceOutcome> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(RemittanceOutcome code) {
-      if (code == RemittanceOutcome.COMPLETE)
+       if (code == RemittanceOutcome.NULL)
+           return null;
+       if (code == RemittanceOutcome.COMPLETE)
         return "complete";
       if (code == RemittanceOutcome.ERROR)
         return "error";
       return "?";
-    }
+   }
 
     public String toSystem(RemittanceOutcome code) {
       return code.getSystem();
@@ -12849,7 +12877,9 @@ public Enumeration<ResourceType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ResourceType code) {
-      if (code == ResourceType.ACCOUNT)
+       if (code == ResourceType.NULL)
+           return null;
+       if (code == ResourceType.ACCOUNT)
         return "Account";
       if (code == ResourceType.ALLERGYINTOLERANCE)
         return "AllergyIntolerance";
@@ -13080,7 +13110,7 @@ public String toCode(ResourceType code) {
       if (code == ResourceType.VISIONPRESCRIPTION)
         return "VisionPrescription";
       return "?";
-    }
+   }
 
     public String toSystem(ResourceType code) {
       return code.getSystem();
@@ -13305,7 +13335,9 @@ public Enumeration<SearchParamType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SearchParamType code) {
-      if (code == SearchParamType.NUMBER)
+       if (code == SearchParamType.NULL)
+           return null;
+       if (code == SearchParamType.NUMBER)
         return "number";
       if (code == SearchParamType.DATE)
         return "date";
@@ -13322,7 +13354,7 @@ public String toCode(SearchParamType code) {
       if (code == SearchParamType.URI)
         return "uri";
       return "?";
-    }
+   }
 
     public String toSystem(SearchParamType code) {
       return code.getSystem();
@@ -13505,7 +13537,9 @@ public Enumeration<SpecialValues> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SpecialValues code) {
-      if (code == SpecialValues.TRUE)
+       if (code == SpecialValues.NULL)
+           return null;
+       if (code == SpecialValues.TRUE)
         return "true";
       if (code == SpecialValues.FALSE)
         return "false";
@@ -13518,7 +13552,7 @@ public String toCode(SpecialValues code) {
       if (code == SpecialValues.NILKNOWN)
         return "nil-known";
       return "?";
-    }
+   }
 
     public String toSystem(SpecialValues code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/EpisodeOfCare.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/EpisodeOfCare.java
index aaffb54cd1..2556d685ea 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/EpisodeOfCare.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/EpisodeOfCare.java
@@ -236,7 +236,9 @@ public Enumeration<EpisodeOfCareStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(EpisodeOfCareStatus code) {
-      if (code == EpisodeOfCareStatus.PLANNED)
+       if (code == EpisodeOfCareStatus.NULL)
+           return null;
+       if (code == EpisodeOfCareStatus.PLANNED)
         return "planned";
       if (code == EpisodeOfCareStatus.WAITLIST)
         return "waitlist";
@@ -249,7 +251,7 @@ public String toCode(EpisodeOfCareStatus code) {
       if (code == EpisodeOfCareStatus.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(EpisodeOfCareStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/FamilyMemberHistory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/FamilyMemberHistory.java
index 069ed81098..15b3a41320 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/FamilyMemberHistory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/FamilyMemberHistory.java
@@ -193,7 +193,9 @@ public Enumeration<FamilyHistoryStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(FamilyHistoryStatus code) {
-      if (code == FamilyHistoryStatus.PARTIAL)
+       if (code == FamilyHistoryStatus.NULL)
+           return null;
+       if (code == FamilyHistoryStatus.PARTIAL)
         return "partial";
       if (code == FamilyHistoryStatus.COMPLETED)
         return "completed";
@@ -202,7 +204,7 @@ public String toCode(FamilyHistoryStatus code) {
       if (code == FamilyHistoryStatus.HEALTHUNKNOWN)
         return "health-unknown";
       return "?";
-    }
+   }
 
     public String toSystem(FamilyHistoryStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Flag.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Flag.java
index 7e078656ef..bc60485c4d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Flag.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Flag.java
@@ -168,14 +168,16 @@ public Enumeration<FlagStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(FlagStatus code) {
-      if (code == FlagStatus.ACTIVE)
+       if (code == FlagStatus.NULL)
+           return null;
+       if (code == FlagStatus.ACTIVE)
         return "active";
       if (code == FlagStatus.INACTIVE)
         return "inactive";
       if (code == FlagStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(FlagStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Goal.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Goal.java
index c86adfadf1..59bc7ecf1b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Goal.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Goal.java
@@ -285,7 +285,9 @@ public Enumeration<GoalStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(GoalStatus code) {
-      if (code == GoalStatus.PROPOSED)
+       if (code == GoalStatus.NULL)
+           return null;
+       if (code == GoalStatus.PROPOSED)
         return "proposed";
       if (code == GoalStatus.PLANNED)
         return "planned";
@@ -304,7 +306,7 @@ public String toCode(GoalStatus code) {
       if (code == GoalStatus.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(GoalStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Group.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Group.java
index e3de17bf6f..8f6a0ad47b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Group.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Group.java
@@ -227,7 +227,9 @@ public Enumeration<GroupType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(GroupType code) {
-      if (code == GroupType.PERSON)
+       if (code == GroupType.NULL)
+           return null;
+       if (code == GroupType.PERSON)
         return "person";
       if (code == GroupType.ANIMAL)
         return "animal";
@@ -240,7 +242,7 @@ public String toCode(GroupType code) {
       if (code == GroupType.SUBSTANCE)
         return "substance";
       return "?";
-    }
+   }
 
     public String toSystem(GroupType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/GuidanceResponse.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/GuidanceResponse.java
index 064c6cb389..dd42379c7e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/GuidanceResponse.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/GuidanceResponse.java
@@ -209,7 +209,9 @@ public Enumeration<GuidanceResponseStatus> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(GuidanceResponseStatus code) {
-      if (code == GuidanceResponseStatus.SUCCESS)
+       if (code == GuidanceResponseStatus.NULL)
+           return null;
+       if (code == GuidanceResponseStatus.SUCCESS)
         return "success";
       if (code == GuidanceResponseStatus.DATAREQUESTED)
         return "data-requested";
@@ -220,7 +222,7 @@ public String toCode(GuidanceResponseStatus code) {
       if (code == GuidanceResponseStatus.FAILURE)
         return "failure";
       return "?";
-    }
+   }
 
     public String toSystem(GuidanceResponseStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HealthcareService.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HealthcareService.java
index 818014db8f..e07e67c6d3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HealthcareService.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HealthcareService.java
@@ -242,7 +242,9 @@ public Enumeration<DaysOfWeek> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DaysOfWeek code) {
-      if (code == DaysOfWeek.MON)
+       if (code == DaysOfWeek.NULL)
+           return null;
+       if (code == DaysOfWeek.MON)
         return "mon";
       if (code == DaysOfWeek.TUE)
         return "tue";
@@ -257,7 +259,7 @@ public String toCode(DaysOfWeek code) {
       if (code == DaysOfWeek.SUN)
         return "sun";
       return "?";
-    }
+   }
 
     public String toSystem(DaysOfWeek code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HumanName.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HumanName.java
index b828ca4c55..042f871eb6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HumanName.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/HumanName.java
@@ -253,7 +253,9 @@ public Enumeration<NameUse> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(NameUse code) {
-      if (code == NameUse.USUAL)
+       if (code == NameUse.NULL)
+           return null;
+       if (code == NameUse.USUAL)
         return "usual";
       if (code == NameUse.OFFICIAL)
         return "official";
@@ -268,7 +270,7 @@ public String toCode(NameUse code) {
       if (code == NameUse.MAIDEN)
         return "maiden";
       return "?";
-    }
+   }
 
     public String toSystem(NameUse code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Identifier.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Identifier.java
index d68532fe33..22e5b950a7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Identifier.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Identifier.java
@@ -188,7 +188,9 @@ public Enumeration<IdentifierUse> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(IdentifierUse code) {
-      if (code == IdentifierUse.USUAL)
+       if (code == IdentifierUse.NULL)
+           return null;
+       if (code == IdentifierUse.USUAL)
         return "usual";
       if (code == IdentifierUse.OFFICIAL)
         return "official";
@@ -197,7 +199,7 @@ public String toCode(IdentifierUse code) {
       if (code == IdentifierUse.SECONDARY)
         return "secondary";
       return "?";
-    }
+   }
 
     public String toSystem(IdentifierUse code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingExcerpt.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingExcerpt.java
index 467bef0e31..3518b46aa4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingExcerpt.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingExcerpt.java
@@ -198,7 +198,9 @@ public Enumeration<DWebType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DWebType code) {
-      if (code == DWebType.WADORS)
+       if (code == DWebType.NULL)
+           return null;
+       if (code == DWebType.WADORS)
         return "WADO-RS";
       if (code == DWebType.WADOURI)
         return "WADO-URI";
@@ -207,7 +209,7 @@ public String toCode(DWebType code) {
       if (code == DWebType.WADOWS)
         return "WADO-WS";
       return "?";
-    }
+   }
 
     public String toSystem(DWebType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingStudy.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingStudy.java
index 53529a236c..f8086df249 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingStudy.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImagingStudy.java
@@ -193,7 +193,9 @@ public Enumeration<InstanceAvailability> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(InstanceAvailability code) {
-      if (code == InstanceAvailability.ONLINE)
+       if (code == InstanceAvailability.NULL)
+           return null;
+       if (code == InstanceAvailability.ONLINE)
         return "ONLINE";
       if (code == InstanceAvailability.OFFLINE)
         return "OFFLINE";
@@ -202,7 +204,7 @@ public String toCode(InstanceAvailability code) {
       if (code == InstanceAvailability.UNAVAILABLE)
         return "UNAVAILABLE";
       return "?";
-    }
+   }
 
     public String toSystem(InstanceAvailability code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImplementationGuide.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImplementationGuide.java
index 25b9f08311..d8341c8e9c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImplementationGuide.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ImplementationGuide.java
@@ -157,12 +157,14 @@ public Enumeration<GuideDependencyType> fromType(Base code) throws FHIRException
     }
 
     public String toCode(GuideDependencyType code) {
-      if (code == GuideDependencyType.REFERENCE)
+       if (code == GuideDependencyType.NULL)
+           return null;
+       if (code == GuideDependencyType.REFERENCE)
         return "reference";
       if (code == GuideDependencyType.INCLUSION)
         return "inclusion";
       return "?";
-    }
+   }
 
     public String toSystem(GuideDependencyType code) {
       return code.getSystem();
@@ -383,7 +385,9 @@ public Enumeration<GuidePageKind> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(GuidePageKind code) {
-      if (code == GuidePageKind.PAGE)
+       if (code == GuidePageKind.NULL)
+           return null;
+       if (code == GuidePageKind.PAGE)
         return "page";
       if (code == GuidePageKind.EXAMPLE)
         return "example";
@@ -400,7 +404,7 @@ public String toCode(GuidePageKind code) {
       if (code == GuidePageKind.RESOURCE)
         return "resource";
       return "?";
-    }
+   }
 
     public String toSystem(GuidePageKind code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Linkage.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Linkage.java
index e788438657..deae2e2efb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Linkage.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Linkage.java
@@ -174,14 +174,16 @@ public Enumeration<LinkageType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(LinkageType code) {
-      if (code == LinkageType.SOURCE)
+       if (code == LinkageType.NULL)
+           return null;
+       if (code == LinkageType.SOURCE)
         return "source";
       if (code == LinkageType.ALTERNATE)
         return "alternate";
       if (code == LinkageType.HISTORICAL)
         return "historical";
       return "?";
-    }
+   }
 
     public String toSystem(LinkageType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ListResource.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ListResource.java
index 8af39ead43..3dd9793726 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ListResource.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ListResource.java
@@ -171,14 +171,16 @@ public Enumeration<ListStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ListStatus code) {
-      if (code == ListStatus.CURRENT)
+       if (code == ListStatus.NULL)
+           return null;
+       if (code == ListStatus.CURRENT)
         return "current";
       if (code == ListStatus.RETIRED)
         return "retired";
       if (code == ListStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(ListStatus code) {
       return code.getSystem();
@@ -307,14 +309,16 @@ public Enumeration<ListMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ListMode code) {
-      if (code == ListMode.WORKING)
+       if (code == ListMode.NULL)
+           return null;
+       if (code == ListMode.WORKING)
         return "working";
       if (code == ListMode.SNAPSHOT)
         return "snapshot";
       if (code == ListMode.CHANGES)
         return "changes";
       return "?";
-    }
+   }
 
     public String toSystem(ListMode code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Location.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Location.java
index 211c3bf451..fc4d50af54 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Location.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Location.java
@@ -174,14 +174,16 @@ public Enumeration<LocationStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(LocationStatus code) {
-      if (code == LocationStatus.ACTIVE)
+       if (code == LocationStatus.NULL)
+           return null;
+       if (code == LocationStatus.ACTIVE)
         return "active";
       if (code == LocationStatus.SUSPENDED)
         return "suspended";
       if (code == LocationStatus.INACTIVE)
         return "inactive";
       return "?";
-    }
+   }
 
     public String toSystem(LocationStatus code) {
       return code.getSystem();
@@ -294,12 +296,14 @@ public Enumeration<LocationMode> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(LocationMode code) {
-      if (code == LocationMode.INSTANCE)
+       if (code == LocationMode.NULL)
+           return null;
+       if (code == LocationMode.INSTANCE)
         return "instance";
       if (code == LocationMode.KIND)
         return "kind";
       return "?";
-    }
+   }
 
     public String toSystem(LocationMode code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Measure.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Measure.java
index 8efb6086a0..077e1017b0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Measure.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Measure.java
@@ -188,7 +188,9 @@ public Enumeration<MeasureScoring> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MeasureScoring code) {
-      if (code == MeasureScoring.PROPORTION)
+       if (code == MeasureScoring.NULL)
+           return null;
+       if (code == MeasureScoring.PROPORTION)
         return "proportion";
       if (code == MeasureScoring.RATIO)
         return "ratio";
@@ -197,7 +199,7 @@ public String toCode(MeasureScoring code) {
       if (code == MeasureScoring.COHORT)
         return "cohort";
       return "?";
-    }
+   }
 
     public String toSystem(MeasureScoring code) {
       return code.getSystem();
@@ -307,12 +309,14 @@ public Enumeration<MeasureType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MeasureType code) {
-      if (code == MeasureType.PROCESS)
+       if (code == MeasureType.NULL)
+           return null;
+       if (code == MeasureType.PROCESS)
         return "process";
       if (code == MeasureType.OUTCOME)
         return "outcome";
       return "?";
-    }
+   }
 
     public String toSystem(MeasureType code) {
       return code.getSystem();
@@ -548,7 +552,9 @@ public Enumeration<MeasurePopulationType> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(MeasurePopulationType code) {
-      if (code == MeasurePopulationType.INITIALPOPULATION)
+       if (code == MeasurePopulationType.NULL)
+           return null;
+       if (code == MeasurePopulationType.INITIALPOPULATION)
         return "initial-population";
       if (code == MeasurePopulationType.NUMERATOR)
         return "numerator";
@@ -567,7 +573,7 @@ public String toCode(MeasurePopulationType code) {
       if (code == MeasurePopulationType.MEASURESCORE)
         return "measure-score";
       return "?";
-    }
+   }
 
     public String toSystem(MeasurePopulationType code) {
       return code.getSystem();
@@ -679,12 +685,14 @@ public Enumeration<MeasureDataUsage> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MeasureDataUsage code) {
-      if (code == MeasureDataUsage.SUPPLEMENTALDATA)
+       if (code == MeasureDataUsage.NULL)
+           return null;
+       if (code == MeasureDataUsage.SUPPLEMENTALDATA)
         return "supplemental-data";
       if (code == MeasureDataUsage.RISKADJUSTMENTFACTOR)
         return "risk-adjustment-factor";
       return "?";
-    }
+   }
 
     public String toSystem(MeasureDataUsage code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MeasureReport.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MeasureReport.java
index 981af916e2..bdb9b0492c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MeasureReport.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MeasureReport.java
@@ -175,14 +175,16 @@ public Enumeration<MeasureReportType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(MeasureReportType code) {
-      if (code == MeasureReportType.INDIVIDUAL)
+       if (code == MeasureReportType.NULL)
+           return null;
+       if (code == MeasureReportType.INDIVIDUAL)
         return "individual";
       if (code == MeasureReportType.PATIENTLIST)
         return "patient-list";
       if (code == MeasureReportType.SUMMARY)
         return "summary";
       return "?";
-    }
+   }
 
     public String toSystem(MeasureReportType code) {
       return code.getSystem();
@@ -310,14 +312,16 @@ public Enumeration<MeasureReportStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(MeasureReportStatus code) {
-      if (code == MeasureReportStatus.COMPLETE)
+       if (code == MeasureReportStatus.NULL)
+           return null;
+       if (code == MeasureReportStatus.COMPLETE)
         return "complete";
       if (code == MeasureReportStatus.PENDING)
         return "pending";
       if (code == MeasureReportStatus.ERROR)
         return "error";
       return "?";
-    }
+   }
 
     public String toSystem(MeasureReportStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Media.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Media.java
index dc603cabb0..20edfb7b73 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Media.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Media.java
@@ -170,14 +170,16 @@ public Enumeration<DigitalMediaType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(DigitalMediaType code) {
-      if (code == DigitalMediaType.PHOTO)
+       if (code == DigitalMediaType.NULL)
+           return null;
+       if (code == DigitalMediaType.PHOTO)
         return "photo";
       if (code == DigitalMediaType.VIDEO)
         return "video";
       if (code == DigitalMediaType.AUDIO)
         return "audio";
       return "?";
-    }
+   }
 
     public String toSystem(DigitalMediaType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationAdministration.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationAdministration.java
index 1076c4b0cd..46509a2e50 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationAdministration.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationAdministration.java
@@ -212,7 +212,9 @@ public Enumeration<MedicationAdministrationStatus> fromType(Base code) throws FH
     }
 
     public String toCode(MedicationAdministrationStatus code) {
-      if (code == MedicationAdministrationStatus.INPROGRESS)
+       if (code == MedicationAdministrationStatus.NULL)
+           return null;
+       if (code == MedicationAdministrationStatus.INPROGRESS)
         return "in-progress";
       if (code == MedicationAdministrationStatus.ONHOLD)
         return "on-hold";
@@ -223,7 +225,7 @@ public String toCode(MedicationAdministrationStatus code) {
       if (code == MedicationAdministrationStatus.STOPPED)
         return "stopped";
       return "?";
-    }
+   }
 
     public String toSystem(MedicationAdministrationStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationDispense.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationDispense.java
index 55cfdcd343..664bc58faf 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationDispense.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationDispense.java
@@ -213,7 +213,9 @@ public Enumeration<MedicationDispenseStatus> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(MedicationDispenseStatus code) {
-      if (code == MedicationDispenseStatus.INPROGRESS)
+       if (code == MedicationDispenseStatus.NULL)
+           return null;
+       if (code == MedicationDispenseStatus.INPROGRESS)
         return "in-progress";
       if (code == MedicationDispenseStatus.ONHOLD)
         return "on-hold";
@@ -224,7 +226,7 @@ public String toCode(MedicationDispenseStatus code) {
       if (code == MedicationDispenseStatus.STOPPED)
         return "stopped";
       return "?";
-    }
+   }
 
     public String toSystem(MedicationDispenseStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationOrder.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationOrder.java
index 595ad91c31..3fb725b17b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationOrder.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationOrder.java
@@ -233,7 +233,9 @@ public Enumeration<MedicationOrderStatus> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(MedicationOrderStatus code) {
-      if (code == MedicationOrderStatus.ACTIVE)
+       if (code == MedicationOrderStatus.NULL)
+           return null;
+       if (code == MedicationOrderStatus.ACTIVE)
         return "active";
       if (code == MedicationOrderStatus.ONHOLD)
         return "on-hold";
@@ -246,7 +248,7 @@ public String toCode(MedicationOrderStatus code) {
       if (code == MedicationOrderStatus.DRAFT)
         return "draft";
       return "?";
-    }
+   }
 
     public String toSystem(MedicationOrderStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationStatement.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationStatement.java
index 2834ac78e4..9d3dcb7712 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationStatement.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MedicationStatement.java
@@ -210,7 +210,9 @@ public Enumeration<MedicationStatementStatus> fromType(Base code) throws FHIRExc
     }
 
     public String toCode(MedicationStatementStatus code) {
-      if (code == MedicationStatementStatus.ACTIVE)
+       if (code == MedicationStatementStatus.NULL)
+           return null;
+       if (code == MedicationStatementStatus.ACTIVE)
         return "active";
       if (code == MedicationStatementStatus.COMPLETED)
         return "completed";
@@ -219,7 +221,7 @@ public String toCode(MedicationStatementStatus code) {
       if (code == MedicationStatementStatus.INTENDED)
         return "intended";
       return "?";
-    }
+   }
 
     public String toSystem(MedicationStatementStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MessageHeader.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MessageHeader.java
index 34b0f38571..0bbbd8ca73 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MessageHeader.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/MessageHeader.java
@@ -178,14 +178,16 @@ public Enumeration<ResponseType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ResponseType code) {
-      if (code == ResponseType.OK)
+       if (code == ResponseType.NULL)
+           return null;
+       if (code == ResponseType.OK)
         return "ok";
       if (code == ResponseType.TRANSIENTERROR)
         return "transient-error";
       if (code == ResponseType.FATALERROR)
         return "fatal-error";
       return "?";
-    }
+   }
 
     public String toSystem(ResponseType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ModuleMetadata.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ModuleMetadata.java
index ef6519e479..4f632a5b93 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ModuleMetadata.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ModuleMetadata.java
@@ -210,7 +210,9 @@ public Enumeration<ModuleMetadataType> fromType(Base code) throws FHIRException
     }
 
     public String toCode(ModuleMetadataType code) {
-      if (code == ModuleMetadataType.MODULE)
+       if (code == ModuleMetadataType.NULL)
+           return null;
+       if (code == ModuleMetadataType.MODULE)
         return "module";
       if (code == ModuleMetadataType.LIBRARY)
         return "library";
@@ -221,7 +223,7 @@ public String toCode(ModuleMetadataType code) {
       if (code == ModuleMetadataType.ORDERSET)
         return "order-set";
       return "?";
-    }
+   }
 
     public String toSystem(ModuleMetadataType code) {
       return code.getSystem();
@@ -350,14 +352,16 @@ public Enumeration<ModuleMetadataStatus> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(ModuleMetadataStatus code) {
-      if (code == ModuleMetadataStatus.DRAFT)
+       if (code == ModuleMetadataStatus.NULL)
+           return null;
+       if (code == ModuleMetadataStatus.DRAFT)
         return "draft";
       if (code == ModuleMetadataStatus.ACTIVE)
         return "active";
       if (code == ModuleMetadataStatus.INACTIVE)
         return "inactive";
       return "?";
-    }
+   }
 
     public String toSystem(ModuleMetadataStatus code) {
       return code.getSystem();
@@ -503,7 +507,9 @@ public Enumeration<ModuleMetadataContributorType> fromType(Base code) throws FHI
     }
 
     public String toCode(ModuleMetadataContributorType code) {
-      if (code == ModuleMetadataContributorType.AUTHOR)
+       if (code == ModuleMetadataContributorType.NULL)
+           return null;
+       if (code == ModuleMetadataContributorType.AUTHOR)
         return "author";
       if (code == ModuleMetadataContributorType.EDITOR)
         return "editor";
@@ -512,7 +518,7 @@ public String toCode(ModuleMetadataContributorType code) {
       if (code == ModuleMetadataContributorType.ENDORSER)
         return "endorser";
       return "?";
-    }
+   }
 
     public String toSystem(ModuleMetadataContributorType code) {
       return code.getSystem();
@@ -706,7 +712,9 @@ public Enumeration<ModuleMetadataResourceType> fromType(Base code) throws FHIREx
     }
 
     public String toCode(ModuleMetadataResourceType code) {
-      if (code == ModuleMetadataResourceType.DOCUMENTATION)
+       if (code == ModuleMetadataResourceType.NULL)
+           return null;
+       if (code == ModuleMetadataResourceType.DOCUMENTATION)
         return "documentation";
       if (code == ModuleMetadataResourceType.JUSTIFICATION)
         return "justification";
@@ -719,7 +727,7 @@ public String toCode(ModuleMetadataResourceType code) {
       if (code == ModuleMetadataResourceType.DERIVEDFROM)
         return "derived-from";
       return "?";
-    }
+   }
 
     public String toSystem(ModuleMetadataResourceType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NamingSystem.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NamingSystem.java
index 8beaea44af..81f8f3e483 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NamingSystem.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NamingSystem.java
@@ -178,14 +178,16 @@ public Enumeration<NamingSystemType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(NamingSystemType code) {
-      if (code == NamingSystemType.CODESYSTEM)
+       if (code == NamingSystemType.NULL)
+           return null;
+       if (code == NamingSystemType.CODESYSTEM)
         return "codesystem";
       if (code == NamingSystemType.IDENTIFIER)
         return "identifier";
       if (code == NamingSystemType.ROOT)
         return "root";
       return "?";
-    }
+   }
 
     public String toSystem(NamingSystemType code) {
       return code.getSystem();
@@ -334,7 +336,9 @@ public Enumeration<NamingSystemIdentifierType> fromType(Base code) throws FHIREx
     }
 
     public String toCode(NamingSystemIdentifierType code) {
-      if (code == NamingSystemIdentifierType.OID)
+       if (code == NamingSystemIdentifierType.NULL)
+           return null;
+       if (code == NamingSystemIdentifierType.OID)
         return "oid";
       if (code == NamingSystemIdentifierType.UUID)
         return "uuid";
@@ -343,7 +347,7 @@ public String toCode(NamingSystemIdentifierType code) {
       if (code == NamingSystemIdentifierType.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(NamingSystemIdentifierType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Narrative.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Narrative.java
index f51565516a..ee2b531bfd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Narrative.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Narrative.java
@@ -189,7 +189,9 @@ public Enumeration<NarrativeStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(NarrativeStatus code) {
-      if (code == NarrativeStatus.GENERATED)
+       if (code == NarrativeStatus.NULL)
+           return null;
+       if (code == NarrativeStatus.GENERATED)
         return "generated";
       if (code == NarrativeStatus.EXTENSIONS)
         return "extensions";
@@ -198,7 +200,7 @@ public String toCode(NarrativeStatus code) {
       if (code == NarrativeStatus.EMPTY)
         return "empty";
       return "?";
-    }
+   }
 
     public String toSystem(NarrativeStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NutritionOrder.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NutritionOrder.java
index 29767f9068..412be34c9e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NutritionOrder.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/NutritionOrder.java
@@ -283,7 +283,9 @@ public Enumeration<NutritionOrderStatus> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(NutritionOrderStatus code) {
-      if (code == NutritionOrderStatus.PROPOSED)
+       if (code == NutritionOrderStatus.NULL)
+           return null;
+       if (code == NutritionOrderStatus.PROPOSED)
         return "proposed";
       if (code == NutritionOrderStatus.DRAFT)
         return "draft";
@@ -302,7 +304,7 @@ public String toCode(NutritionOrderStatus code) {
       if (code == NutritionOrderStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(NutritionOrderStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Observation.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Observation.java
index f36361f7a1..5881b48482 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Observation.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Observation.java
@@ -251,7 +251,9 @@ public Enumeration<ObservationStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ObservationStatus code) {
-      if (code == ObservationStatus.REGISTERED)
+       if (code == ObservationStatus.NULL)
+           return null;
+       if (code == ObservationStatus.REGISTERED)
         return "registered";
       if (code == ObservationStatus.PRELIMINARY)
         return "preliminary";
@@ -266,7 +268,7 @@ public String toCode(ObservationStatus code) {
       if (code == ObservationStatus.UNKNOWN)
         return "unknown";
       return "?";
-    }
+   }
 
     public String toSystem(ObservationStatus code) {
       return code.getSystem();
@@ -458,7 +460,9 @@ public Enumeration<ObservationRelationshipType> fromType(Base code) throws FHIRE
     }
 
     public String toCode(ObservationRelationshipType code) {
-      if (code == ObservationRelationshipType.HASMEMBER)
+       if (code == ObservationRelationshipType.NULL)
+           return null;
+       if (code == ObservationRelationshipType.HASMEMBER)
         return "has-member";
       if (code == ObservationRelationshipType.DERIVEDFROM)
         return "derived-from";
@@ -471,7 +475,7 @@ public String toCode(ObservationRelationshipType code) {
       if (code == ObservationRelationshipType.INTERFEREDBY)
         return "interfered-by";
       return "?";
-    }
+   }
 
     public String toSystem(ObservationRelationshipType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationDefinition.java
index b90650aa00..b4c60b2d96 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationDefinition.java
@@ -160,12 +160,14 @@ public Enumeration<OperationKind> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(OperationKind code) {
-      if (code == OperationKind.OPERATION)
+       if (code == OperationKind.NULL)
+           return null;
+       if (code == OperationKind.OPERATION)
         return "operation";
       if (code == OperationKind.QUERY)
         return "query";
       return "?";
-    }
+   }
 
     public String toSystem(OperationKind code) {
       return code.getSystem();
@@ -275,12 +277,14 @@ public Enumeration<OperationParameterUse> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(OperationParameterUse code) {
-      if (code == OperationParameterUse.IN)
+       if (code == OperationParameterUse.NULL)
+           return null;
+       if (code == OperationParameterUse.IN)
         return "in";
       if (code == OperationParameterUse.OUT)
         return "out";
       return "?";
-    }
+   }
 
     public String toSystem(OperationParameterUse code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationOutcome.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationOutcome.java
index 4d5b93abb8..feefcf37ae 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationOutcome.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OperationOutcome.java
@@ -191,7 +191,9 @@ public Enumeration<IssueSeverity> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(IssueSeverity code) {
-      if (code == IssueSeverity.FATAL)
+       if (code == IssueSeverity.NULL)
+           return null;
+       if (code == IssueSeverity.FATAL)
         return "fatal";
       if (code == IssueSeverity.ERROR)
         return "error";
@@ -200,7 +202,7 @@ public String toCode(IssueSeverity code) {
       if (code == IssueSeverity.INFORMATION)
         return "information";
       return "?";
-    }
+   }
 
     public String toSystem(IssueSeverity code) {
       return code.getSystem();
@@ -816,7 +818,9 @@ public Enumeration<IssueType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(IssueType code) {
-      if (code == IssueType.INVALID)
+       if (code == IssueType.NULL)
+           return null;
+       if (code == IssueType.INVALID)
         return "invalid";
       if (code == IssueType.STRUCTURE)
         return "structure";
@@ -875,7 +879,7 @@ public String toCode(IssueType code) {
       if (code == IssueType.INFORMATIONAL)
         return "informational";
       return "?";
-    }
+   }
 
     public String toSystem(IssueType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OrderResponse.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OrderResponse.java
index b5ddf4434d..24d9d83813 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OrderResponse.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/OrderResponse.java
@@ -280,7 +280,9 @@ public Enumeration<OrderStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(OrderStatus code) {
-      if (code == OrderStatus.PENDING)
+       if (code == OrderStatus.NULL)
+           return null;
+       if (code == OrderStatus.PENDING)
         return "pending";
       if (code == OrderStatus.REVIEW)
         return "review";
@@ -299,7 +301,7 @@ public String toCode(OrderStatus code) {
       if (code == OrderStatus.COMPLETED)
         return "completed";
       return "?";
-    }
+   }
 
     public String toSystem(OrderStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Patient.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Patient.java
index 2169cf3e52..cbdd25183f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Patient.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Patient.java
@@ -182,14 +182,16 @@ public Enumeration<LinkType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(LinkType code) {
-      if (code == LinkType.REPLACE)
+       if (code == LinkType.NULL)
+           return null;
+       if (code == LinkType.REPLACE)
         return "replace";
       if (code == LinkType.REFER)
         return "refer";
       if (code == LinkType.SEEALSO)
         return "seealso";
       return "?";
-    }
+   }
 
     public String toSystem(LinkType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Person.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Person.java
index 38a6acf7d3..1850b69a80 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Person.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Person.java
@@ -191,7 +191,9 @@ public Enumeration<IdentityAssuranceLevel> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(IdentityAssuranceLevel code) {
-      if (code == IdentityAssuranceLevel.LEVEL1)
+       if (code == IdentityAssuranceLevel.NULL)
+           return null;
+       if (code == IdentityAssuranceLevel.LEVEL1)
         return "level1";
       if (code == IdentityAssuranceLevel.LEVEL2)
         return "level2";
@@ -200,7 +202,7 @@ public String toCode(IdentityAssuranceLevel code) {
       if (code == IdentityAssuranceLevel.LEVEL4)
         return "level4";
       return "?";
-    }
+   }
 
     public String toSystem(IdentityAssuranceLevel code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Procedure.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Procedure.java
index ddbfc23cbf..d4f71f60c4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Procedure.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Procedure.java
@@ -189,7 +189,9 @@ public Enumeration<ProcedureStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ProcedureStatus code) {
-      if (code == ProcedureStatus.INPROGRESS)
+       if (code == ProcedureStatus.NULL)
+           return null;
+       if (code == ProcedureStatus.INPROGRESS)
         return "in-progress";
       if (code == ProcedureStatus.ABORTED)
         return "aborted";
@@ -198,7 +200,7 @@ public String toCode(ProcedureStatus code) {
       if (code == ProcedureStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(ProcedureStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcedureRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcedureRequest.java
index 07f223a75c..dea9ec59b9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcedureRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcedureRequest.java
@@ -298,7 +298,9 @@ public Enumeration<ProcedureRequestStatus> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(ProcedureRequestStatus code) {
-      if (code == ProcedureRequestStatus.PROPOSED)
+       if (code == ProcedureRequestStatus.NULL)
+           return null;
+       if (code == ProcedureRequestStatus.PROPOSED)
         return "proposed";
       if (code == ProcedureRequestStatus.DRAFT)
         return "draft";
@@ -319,7 +321,7 @@ public String toCode(ProcedureRequestStatus code) {
       if (code == ProcedureRequestStatus.ABORTED)
         return "aborted";
       return "?";
-    }
+   }
 
     public String toSystem(ProcedureRequestStatus code) {
       return code.getSystem();
@@ -465,7 +467,9 @@ public Enumeration<ProcedureRequestPriority> fromType(Base code) throws FHIRExce
     }
 
     public String toCode(ProcedureRequestPriority code) {
-      if (code == ProcedureRequestPriority.ROUTINE)
+       if (code == ProcedureRequestPriority.NULL)
+           return null;
+       if (code == ProcedureRequestPriority.ROUTINE)
         return "routine";
       if (code == ProcedureRequestPriority.URGENT)
         return "urgent";
@@ -474,7 +478,7 @@ public String toCode(ProcedureRequestPriority code) {
       if (code == ProcedureRequestPriority.ASAP)
         return "asap";
       return "?";
-    }
+   }
 
     public String toSystem(ProcedureRequestPriority code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcessRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcessRequest.java
index eb47c9567b..21683b1ec3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcessRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ProcessRequest.java
@@ -190,7 +190,9 @@ public Enumeration<ActionList> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ActionList code) {
-      if (code == ActionList.CANCEL)
+       if (code == ActionList.NULL)
+           return null;
+       if (code == ActionList.CANCEL)
         return "cancel";
       if (code == ActionList.POLL)
         return "poll";
@@ -199,7 +201,7 @@ public String toCode(ActionList code) {
       if (code == ActionList.STATUS)
         return "status";
       return "?";
-    }
+   }
 
     public String toSystem(ActionList code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Protocol.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Protocol.java
index 161962cebc..48d48d2ea4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Protocol.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Protocol.java
@@ -228,7 +228,9 @@ public Enumeration<ProtocolStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ProtocolStatus code) {
-      if (code == ProtocolStatus.DRAFT)
+       if (code == ProtocolStatus.NULL)
+           return null;
+       if (code == ProtocolStatus.DRAFT)
         return "draft";
       if (code == ProtocolStatus.TESTING)
         return "testing";
@@ -241,7 +243,7 @@ public String toCode(ProtocolStatus code) {
       if (code == ProtocolStatus.SUPERSEDED)
         return "superseded";
       return "?";
-    }
+   }
 
     public String toSystem(ProtocolStatus code) {
       return code.getSystem();
@@ -391,7 +393,9 @@ public Enumeration<ProtocolType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ProtocolType code) {
-      if (code == ProtocolType.CONDITION)
+       if (code == ProtocolType.NULL)
+           return null;
+       if (code == ProtocolType.CONDITION)
         return "condition";
       if (code == ProtocolType.DEVICE)
         return "device";
@@ -400,7 +404,7 @@ public String toCode(ProtocolType code) {
       if (code == ProtocolType.STUDY)
         return "study";
       return "?";
-    }
+   }
 
     public String toSystem(ProtocolType code) {
       return code.getSystem();
@@ -603,7 +607,9 @@ public Enumeration<ActivityDefinitionCategory> fromType(Base code) throws FHIREx
     }
 
     public String toCode(ActivityDefinitionCategory code) {
-      if (code == ActivityDefinitionCategory.DIET)
+       if (code == ActivityDefinitionCategory.NULL)
+           return null;
+       if (code == ActivityDefinitionCategory.DIET)
         return "diet";
       if (code == ActivityDefinitionCategory.DRUG)
         return "drug";
@@ -618,7 +624,7 @@ public String toCode(ActivityDefinitionCategory code) {
       if (code == ActivityDefinitionCategory.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(ActivityDefinitionCategory code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Provenance.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Provenance.java
index 1091787e20..f5aaaf5716 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Provenance.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Provenance.java
@@ -223,7 +223,9 @@ public Enumeration<ProvenanceEntityRole> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(ProvenanceEntityRole code) {
-      if (code == ProvenanceEntityRole.DERIVATION)
+       if (code == ProvenanceEntityRole.NULL)
+           return null;
+       if (code == ProvenanceEntityRole.DERIVATION)
         return "derivation";
       if (code == ProvenanceEntityRole.REVISION)
         return "revision";
@@ -234,7 +236,7 @@ public String toCode(ProvenanceEntityRole code) {
       if (code == ProvenanceEntityRole.REMOVAL)
         return "removal";
       return "?";
-    }
+   }
 
     public String toSystem(ProvenanceEntityRole code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Quantity.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Quantity.java
index 1e03bcb31d..d8665276ad 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Quantity.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Quantity.java
@@ -189,7 +189,9 @@ public Enumeration<QuantityComparator> fromType(Base code) throws FHIRException
     }
 
     public String toCode(QuantityComparator code) {
-      if (code == QuantityComparator.LESS_THAN)
+       if (code == QuantityComparator.NULL)
+           return null;
+       if (code == QuantityComparator.LESS_THAN)
         return "<";
       if (code == QuantityComparator.LESS_OR_EQUAL)
         return "<=";
@@ -198,7 +200,7 @@ public String toCode(QuantityComparator code) {
       if (code == QuantityComparator.GREATER_THAN)
         return ">";
       return "?";
-    }
+   }
 
     public String toSystem(QuantityComparator code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Questionnaire.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Questionnaire.java
index 103e36a854..f245d6a1eb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Questionnaire.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Questionnaire.java
@@ -173,14 +173,16 @@ public Enumeration<QuestionnaireStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(QuestionnaireStatus code) {
-      if (code == QuestionnaireStatus.DRAFT)
+       if (code == QuestionnaireStatus.NULL)
+           return null;
+       if (code == QuestionnaireStatus.DRAFT)
         return "draft";
       if (code == QuestionnaireStatus.PUBLISHED)
         return "published";
       if (code == QuestionnaireStatus.RETIRED)
         return "retired";
       return "?";
-    }
+   }
 
     public String toSystem(QuestionnaireStatus code) {
       return code.getSystem();
@@ -584,7 +586,9 @@ public Enumeration<QuestionnaireItemType> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(QuestionnaireItemType code) {
-      if (code == QuestionnaireItemType.GROUP)
+       if (code == QuestionnaireItemType.NULL)
+           return null;
+       if (code == QuestionnaireItemType.GROUP)
         return "group";
       if (code == QuestionnaireItemType.DISPLAY)
         return "display";
@@ -621,7 +625,7 @@ public String toCode(QuestionnaireItemType code) {
       if (code == QuestionnaireItemType.QUANTITY)
         return "quantity";
       return "?";
-    }
+   }
 
     public String toSystem(QuestionnaireItemType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/QuestionnaireResponse.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/QuestionnaireResponse.java
index 6c49ea0249..12126dbeb3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/QuestionnaireResponse.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/QuestionnaireResponse.java
@@ -176,14 +176,16 @@ public Enumeration<QuestionnaireResponseStatus> fromType(Base code) throws FHIRE
     }
 
     public String toCode(QuestionnaireResponseStatus code) {
-      if (code == QuestionnaireResponseStatus.INPROGRESS)
+       if (code == QuestionnaireResponseStatus.NULL)
+           return null;
+       if (code == QuestionnaireResponseStatus.INPROGRESS)
         return "in-progress";
       if (code == QuestionnaireResponseStatus.COMPLETED)
         return "completed";
       if (code == QuestionnaireResponseStatus.AMENDED)
         return "amended";
       return "?";
-    }
+   }
 
     public String toSystem(QuestionnaireResponseStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ReferralRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ReferralRequest.java
index 2fe1de6a8e..e8a7b76ba4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ReferralRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ReferralRequest.java
@@ -210,7 +210,9 @@ public Enumeration<ReferralStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ReferralStatus code) {
-      if (code == ReferralStatus.DRAFT)
+       if (code == ReferralStatus.NULL)
+           return null;
+       if (code == ReferralStatus.DRAFT)
         return "draft";
       if (code == ReferralStatus.ACTIVE)
         return "active";
@@ -221,7 +223,7 @@ public String toCode(ReferralStatus code) {
       if (code == ReferralStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(ReferralStatus code) {
       return code.getSystem();
@@ -352,14 +354,16 @@ public Enumeration<ReferralCategory> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ReferralCategory code) {
-      if (code == ReferralCategory.PROPOSAL)
+       if (code == ReferralCategory.NULL)
+           return null;
+       if (code == ReferralCategory.PROPOSAL)
         return "proposal";
       if (code == ReferralCategory.PLAN)
         return "plan";
       if (code == ReferralCategory.REQUEST)
         return "request";
       return "?";
-    }
+   }
 
     public String toSystem(ReferralCategory code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SearchParameter.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SearchParameter.java
index f1059134ea..3071aa372b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SearchParameter.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SearchParameter.java
@@ -216,7 +216,9 @@ public Enumeration<XPathUsageType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(XPathUsageType code) {
-      if (code == XPathUsageType.NORMAL)
+       if (code == XPathUsageType.NULL)
+           return null;
+       if (code == XPathUsageType.NORMAL)
         return "normal";
       if (code == XPathUsageType.PHONETIC)
         return "phonetic";
@@ -227,7 +229,7 @@ public String toCode(XPathUsageType code) {
       if (code == XPathUsageType.OTHER)
         return "other";
       return "?";
-    }
+   }
 
     public String toSystem(XPathUsageType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Sequence.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Sequence.java
index 61365e1070..9b00857f20 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Sequence.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Sequence.java
@@ -172,14 +172,16 @@ public Enumeration<SequenceType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SequenceType code) {
-      if (code == SequenceType.AA)
+       if (code == SequenceType.NULL)
+           return null;
+       if (code == SequenceType.AA)
         return "AA";
       if (code == SequenceType.DNA)
         return "DNA";
       if (code == SequenceType.RNA)
         return "RNA";
       return "?";
-    }
+   }
 
     public String toSystem(SequenceType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Slot.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Slot.java
index a2513a13c4..5fe641a8b6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Slot.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Slot.java
@@ -190,7 +190,9 @@ public Enumeration<SlotStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SlotStatus code) {
-      if (code == SlotStatus.BUSY)
+       if (code == SlotStatus.NULL)
+           return null;
+       if (code == SlotStatus.BUSY)
         return "busy";
       if (code == SlotStatus.FREE)
         return "free";
@@ -199,7 +201,7 @@ public String toCode(SlotStatus code) {
       if (code == SlotStatus.BUSYTENTATIVE)
         return "busy-tentative";
       return "?";
-    }
+   }
 
     public String toSystem(SlotStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Specimen.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Specimen.java
index 831de516f5..c34b59d8d2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Specimen.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Specimen.java
@@ -191,7 +191,9 @@ public Enumeration<SpecimenStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(SpecimenStatus code) {
-      if (code == SpecimenStatus.AVAILABLE)
+       if (code == SpecimenStatus.NULL)
+           return null;
+       if (code == SpecimenStatus.AVAILABLE)
         return "available";
       if (code == SpecimenStatus.UNAVAILABLE)
         return "unavailable";
@@ -200,7 +202,7 @@ public String toCode(SpecimenStatus code) {
       if (code == SpecimenStatus.ENTEREDINERROR)
         return "entered-in-error";
       return "?";
-    }
+   }
 
     public String toSystem(SpecimenStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureDefinition.java
index 7ec1f03883..f889d7801d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureDefinition.java
@@ -178,14 +178,16 @@ public Enumeration<StructureDefinitionKind> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(StructureDefinitionKind code) {
-      if (code == StructureDefinitionKind.DATATYPE)
+       if (code == StructureDefinitionKind.NULL)
+           return null;
+       if (code == StructureDefinitionKind.DATATYPE)
         return "datatype";
       if (code == StructureDefinitionKind.RESOURCE)
         return "resource";
       if (code == StructureDefinitionKind.LOGICAL)
         return "logical";
       return "?";
-    }
+   }
 
     public String toSystem(StructureDefinitionKind code) {
       return code.getSystem();
@@ -316,14 +318,16 @@ public Enumeration<ExtensionContext> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ExtensionContext code) {
-      if (code == ExtensionContext.RESOURCE)
+       if (code == ExtensionContext.NULL)
+           return null;
+       if (code == ExtensionContext.RESOURCE)
         return "resource";
       if (code == ExtensionContext.DATATYPE)
         return "datatype";
       if (code == ExtensionContext.EXTENSION)
         return "extension";
       return "?";
-    }
+   }
 
     public String toSystem(ExtensionContext code) {
       return code.getSystem();
@@ -434,12 +438,14 @@ public Enumeration<TypeDerivationRule> fromType(Base code) throws FHIRException
     }
 
     public String toCode(TypeDerivationRule code) {
-      if (code == TypeDerivationRule.SPECIALIZATION)
+       if (code == TypeDerivationRule.NULL)
+           return null;
+       if (code == TypeDerivationRule.SPECIALIZATION)
         return "specialization";
       if (code == TypeDerivationRule.CONSTRAINT)
         return "constraint";
       return "?";
-    }
+   }
 
     public String toSystem(TypeDerivationRule code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureMap.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureMap.java
index ba7e491978..137a8405d9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureMap.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/StructureMap.java
@@ -196,7 +196,9 @@ public Enumeration<StructureMapModelMode> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(StructureMapModelMode code) {
-      if (code == StructureMapModelMode.SOURCE)
+       if (code == StructureMapModelMode.NULL)
+           return null;
+       if (code == StructureMapModelMode.SOURCE)
         return "source";
       if (code == StructureMapModelMode.QUERIED)
         return "queried";
@@ -205,7 +207,7 @@ public String toCode(StructureMapModelMode code) {
       if (code == StructureMapModelMode.PRODUCED)
         return "produced";
       return "?";
-    }
+   }
 
     public String toSystem(StructureMapModelMode code) {
       return code.getSystem();
@@ -315,12 +317,14 @@ public Enumeration<StructureMapInputMode> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(StructureMapInputMode code) {
-      if (code == StructureMapInputMode.SOURCE)
+       if (code == StructureMapInputMode.NULL)
+           return null;
+       if (code == StructureMapInputMode.SOURCE)
         return "source";
       if (code == StructureMapInputMode.TARGET)
         return "target";
       return "?";
-    }
+   }
 
     public String toSystem(StructureMapInputMode code) {
       return code.getSystem();
@@ -430,12 +434,14 @@ public Enumeration<StructureMapContextType> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(StructureMapContextType code) {
-      if (code == StructureMapContextType.TYPE)
+       if (code == StructureMapContextType.NULL)
+           return null;
+       if (code == StructureMapContextType.TYPE)
         return "type";
       if (code == StructureMapContextType.VARIABLE)
         return "variable";
       return "?";
-    }
+   }
 
     public String toSystem(StructureMapContextType code) {
       return code.getSystem();
@@ -568,14 +574,16 @@ public Enumeration<StructureMapListMode> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(StructureMapListMode code) {
-      if (code == StructureMapListMode.FIRST)
+       if (code == StructureMapListMode.NULL)
+           return null;
+       if (code == StructureMapListMode.FIRST)
         return "first";
       if (code == StructureMapListMode.SHARE)
         return "share";
       if (code == StructureMapListMode.LAST)
         return "last";
       return "?";
-    }
+   }
 
     public String toSystem(StructureMapListMode code) {
       return code.getSystem();
@@ -870,7 +878,9 @@ public Enumeration<StructureMapTransform> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(StructureMapTransform code) {
-      if (code == StructureMapTransform.CREATE)
+       if (code == StructureMapTransform.NULL)
+           return null;
+       if (code == StructureMapTransform.CREATE)
         return "create";
       if (code == StructureMapTransform.COPY)
         return "copy";
@@ -895,7 +905,7 @@ public String toCode(StructureMapTransform code) {
       if (code == StructureMapTransform.EVALUATE)
         return "evaluate";
       return "?";
-    }
+   }
 
     public String toSystem(StructureMapTransform code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Subscription.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Subscription.java
index a3bbf866ee..3acce41337 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Subscription.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Subscription.java
@@ -194,7 +194,9 @@ public Enumeration<SubscriptionStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(SubscriptionStatus code) {
-      if (code == SubscriptionStatus.REQUESTED)
+       if (code == SubscriptionStatus.NULL)
+           return null;
+       if (code == SubscriptionStatus.REQUESTED)
         return "requested";
       if (code == SubscriptionStatus.ACTIVE)
         return "active";
@@ -203,7 +205,7 @@ public String toCode(SubscriptionStatus code) {
       if (code == SubscriptionStatus.OFF)
         return "off";
       return "?";
-    }
+   }
 
     public String toSystem(SubscriptionStatus code) {
       return code.getSystem();
@@ -374,7 +376,9 @@ public Enumeration<SubscriptionChannelType> fromType(Base code) throws FHIRExcep
     }
 
     public String toCode(SubscriptionChannelType code) {
-      if (code == SubscriptionChannelType.RESTHOOK)
+       if (code == SubscriptionChannelType.NULL)
+           return null;
+       if (code == SubscriptionChannelType.RESTHOOK)
         return "rest-hook";
       if (code == SubscriptionChannelType.WEBSOCKET)
         return "websocket";
@@ -385,7 +389,7 @@ public String toCode(SubscriptionChannelType code) {
       if (code == SubscriptionChannelType.MESSAGE)
         return "message";
       return "?";
-    }
+   }
 
     public String toSystem(SubscriptionChannelType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyDelivery.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyDelivery.java
index 3e4c0f8edc..fc755e6019 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyDelivery.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyDelivery.java
@@ -168,14 +168,16 @@ public Enumeration<SupplyDeliveryStatus> fromType(Base code) throws FHIRExceptio
     }
 
     public String toCode(SupplyDeliveryStatus code) {
-      if (code == SupplyDeliveryStatus.INPROGRESS)
+       if (code == SupplyDeliveryStatus.NULL)
+           return null;
+       if (code == SupplyDeliveryStatus.INPROGRESS)
         return "in-progress";
       if (code == SupplyDeliveryStatus.COMPLETED)
         return "completed";
       if (code == SupplyDeliveryStatus.ABANDONED)
         return "abandoned";
       return "?";
-    }
+   }
 
     public String toSystem(SupplyDeliveryStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyRequest.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyRequest.java
index 7e2b0295a6..136382f51a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyRequest.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/SupplyRequest.java
@@ -190,7 +190,9 @@ public Enumeration<SupplyRequestStatus> fromType(Base code) throws FHIRException
     }
 
     public String toCode(SupplyRequestStatus code) {
-      if (code == SupplyRequestStatus.REQUESTED)
+       if (code == SupplyRequestStatus.NULL)
+           return null;
+       if (code == SupplyRequestStatus.REQUESTED)
         return "requested";
       if (code == SupplyRequestStatus.COMPLETED)
         return "completed";
@@ -199,7 +201,7 @@ public String toCode(SupplyRequestStatus code) {
       if (code == SupplyRequestStatus.CANCELLED)
         return "cancelled";
       return "?";
-    }
+   }
 
     public String toSystem(SupplyRequestStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Task.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Task.java
index 1b29117191..aebd31fe47 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Task.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Task.java
@@ -171,14 +171,16 @@ public Enumeration<TaskPriority> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(TaskPriority code) {
-      if (code == TaskPriority.LOW)
+       if (code == TaskPriority.NULL)
+           return null;
+       if (code == TaskPriority.LOW)
         return "low";
       if (code == TaskPriority.NORMAL)
         return "normal";
       if (code == TaskPriority.HIGH)
         return "high";
       return "?";
-    }
+   }
 
     public String toSystem(TaskPriority code) {
       return code.getSystem();
@@ -437,7 +439,9 @@ public Enumeration<TaskStatus> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(TaskStatus code) {
-      if (code == TaskStatus.DRAFT)
+       if (code == TaskStatus.NULL)
+           return null;
+       if (code == TaskStatus.DRAFT)
         return "draft";
       if (code == TaskStatus.REQUESTED)
         return "requested";
@@ -458,7 +462,7 @@ public String toCode(TaskStatus code) {
       if (code == TaskStatus.COMPLETED)
         return "completed";
       return "?";
-    }
+   }
 
     public String toSystem(TaskStatus code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TestScript.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TestScript.java
index e96020bab7..3e12fe3ee6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TestScript.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TestScript.java
@@ -156,12 +156,14 @@ public Enumeration<ContentType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(ContentType code) {
-      if (code == ContentType.XML)
+       if (code == ContentType.NULL)
+           return null;
+       if (code == ContentType.XML)
         return "xml";
       if (code == ContentType.JSON)
         return "json";
       return "?";
-    }
+   }
 
     public String toSystem(ContentType code) {
       return code.getSystem();
@@ -271,12 +273,14 @@ public Enumeration<AssertionDirectionType> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(AssertionDirectionType code) {
-      if (code == AssertionDirectionType.RESPONSE)
+       if (code == AssertionDirectionType.NULL)
+           return null;
+       if (code == AssertionDirectionType.RESPONSE)
         return "response";
       if (code == AssertionDirectionType.REQUEST)
         return "request";
       return "?";
-    }
+   }
 
     public String toSystem(AssertionDirectionType code) {
       return code.getSystem();
@@ -530,7 +534,9 @@ public Enumeration<AssertionOperatorType> fromType(Base code) throws FHIRExcepti
     }
 
     public String toCode(AssertionOperatorType code) {
-      if (code == AssertionOperatorType.EQUALS)
+       if (code == AssertionOperatorType.NULL)
+           return null;
+       if (code == AssertionOperatorType.EQUALS)
         return "equals";
       if (code == AssertionOperatorType.NOTEQUALS)
         return "notEquals";
@@ -551,7 +557,7 @@ public String toCode(AssertionOperatorType code) {
       if (code == AssertionOperatorType.NOTCONTAINS)
         return "notContains";
       return "?";
-    }
+   }
 
     public String toSystem(AssertionOperatorType code) {
       return code.getSystem();
@@ -841,7 +847,9 @@ public Enumeration<AssertionResponseTypes> fromType(Base code) throws FHIRExcept
     }
 
     public String toCode(AssertionResponseTypes code) {
-      if (code == AssertionResponseTypes.OKAY)
+       if (code == AssertionResponseTypes.NULL)
+           return null;
+       if (code == AssertionResponseTypes.OKAY)
         return "okay";
       if (code == AssertionResponseTypes.CREATED)
         return "created";
@@ -866,7 +874,7 @@ public String toCode(AssertionResponseTypes code) {
       if (code == AssertionResponseTypes.UNPROCESSABLE)
         return "unprocessable";
       return "?";
-    }
+   }
 
     public String toSystem(AssertionResponseTypes code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Timing.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Timing.java
index 104e977e71..a109aabcf8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Timing.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/Timing.java
@@ -247,7 +247,9 @@ public Enumeration<UnitsOfTime> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(UnitsOfTime code) {
-      if (code == UnitsOfTime.S)
+       if (code == UnitsOfTime.NULL)
+           return null;
+       if (code == UnitsOfTime.S)
         return "s";
       if (code == UnitsOfTime.MIN)
         return "min";
@@ -262,7 +264,7 @@ public String toCode(UnitsOfTime code) {
       if (code == UnitsOfTime.A)
         return "a";
       return "?";
-    }
+   }
 
     public String toSystem(UnitsOfTime code) {
       return code.getSystem();
@@ -588,7 +590,9 @@ public Enumeration<EventTiming> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(EventTiming code) {
-      if (code == EventTiming.HS)
+       if (code == EventTiming.NULL)
+           return null;
+       if (code == EventTiming.HS)
         return "HS";
       if (code == EventTiming.WAKE)
         return "WAKE";
@@ -617,7 +621,7 @@ public String toCode(EventTiming code) {
       if (code == EventTiming.PCV)
         return "PCV";
       return "?";
-    }
+   }
 
     public String toSystem(EventTiming code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TriggerDefinition.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TriggerDefinition.java
index 974ebda085..95453bcaf7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TriggerDefinition.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/TriggerDefinition.java
@@ -240,7 +240,9 @@ public Enumeration<TriggerType> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(TriggerType code) {
-      if (code == TriggerType.NAMEDEVENT)
+       if (code == TriggerType.NULL)
+           return null;
+       if (code == TriggerType.NAMEDEVENT)
         return "named-event";
       if (code == TriggerType.PERIODIC)
         return "periodic";
@@ -255,7 +257,7 @@ public String toCode(TriggerType code) {
       if (code == TriggerType.DATAACCESSENDED)
         return "data-access-ended";
       return "?";
-    }
+   }
 
     public String toSystem(TriggerType code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ValueSet.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ValueSet.java
index d839b2dd19..6143f8ee49 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ValueSet.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/ValueSet.java
@@ -232,7 +232,9 @@ public Enumeration<FilterOperator> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(FilterOperator code) {
-      if (code == FilterOperator.EQUAL)
+       if (code == FilterOperator.NULL)
+           return null;
+       if (code == FilterOperator.EQUAL)
         return "=";
       if (code == FilterOperator.ISA)
         return "is-a";
@@ -245,7 +247,7 @@ public String toCode(FilterOperator code) {
       if (code == FilterOperator.NOTIN)
         return "not-in";
       return "?";
-    }
+   }
 
     public String toSystem(FilterOperator code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/VisionPrescription.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/VisionPrescription.java
index db527aa332..4c05a2e9bf 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/VisionPrescription.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/VisionPrescription.java
@@ -156,12 +156,14 @@ public Enumeration<VisionEyes> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(VisionEyes code) {
-      if (code == VisionEyes.RIGHT)
+       if (code == VisionEyes.NULL)
+           return null;
+       if (code == VisionEyes.RIGHT)
         return "right";
       if (code == VisionEyes.LEFT)
         return "left";
       return "?";
-    }
+   }
 
     public String toSystem(VisionEyes code) {
       return code.getSystem();
@@ -307,7 +309,9 @@ public Enumeration<VisionBase> fromType(Base code) throws FHIRException {
     }
 
     public String toCode(VisionBase code) {
-      if (code == VisionBase.UP)
+       if (code == VisionBase.NULL)
+           return null;
+       if (code == VisionBase.UP)
         return "up";
       if (code == VisionBase.DOWN)
         return "down";
@@ -316,7 +320,7 @@ public String toCode(VisionBase code) {
       if (code == VisionBase.OUT)
         return "out";
       return "?";
-    }
+   }
 
     public String toSystem(VisionBase code) {
       return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AbstractTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AbstractTypesEnumFactory.java
index 7226998a64..60e36924f8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AbstractTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AbstractTypesEnumFactory.java
@@ -46,12 +46,14 @@ public AbstractTypes fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(AbstractTypes code) {
-    if (code == AbstractTypes.TYPE)
+       if (code == AbstractTypes.NULL)
+           return null;
+       if (code == AbstractTypes.TYPE)
       return "Type";
     if (code == AbstractTypes.ANY)
       return "Any";
     return "?";
-  }
+   }
 
   public String toSystem(AbstractTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AccountStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AccountStatusEnumFactory.java
index 9af6cf36ec..9490cf2b51 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AccountStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AccountStatusEnumFactory.java
@@ -46,12 +46,14 @@ public AccountStatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(AccountStatus code) {
-    if (code == AccountStatus.ACTIVE)
+       if (code == AccountStatus.NULL)
+           return null;
+       if (code == AccountStatus.ACTIVE)
       return "active";
     if (code == AccountStatus.INACTIVE)
       return "inactive";
     return "?";
-  }
+   }
 
   public String toSystem(AccountStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionBehaviorTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionBehaviorTypeEnumFactory.java
index 998ff29f48..8a89b665dd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionBehaviorTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionBehaviorTypeEnumFactory.java
@@ -52,7 +52,9 @@ public ActionBehaviorType fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ActionBehaviorType code) {
-    if (code == ActionBehaviorType.GROUPING)
+       if (code == ActionBehaviorType.NULL)
+           return null;
+       if (code == ActionBehaviorType.GROUPING)
       return "grouping";
     if (code == ActionBehaviorType.SELECTION)
       return "selection";
@@ -63,7 +65,7 @@ public String toCode(ActionBehaviorType code) {
     if (code == ActionBehaviorType.CARDINALITY)
       return "cardinality";
     return "?";
-  }
+   }
 
   public String toSystem(ActionBehaviorType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionCardinalityBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionCardinalityBehaviorEnumFactory.java
index aece6daf51..ffac218a8d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionCardinalityBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionCardinalityBehaviorEnumFactory.java
@@ -46,12 +46,14 @@ public ActionCardinalityBehavior fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(ActionCardinalityBehavior code) {
-    if (code == ActionCardinalityBehavior.SINGLE)
+       if (code == ActionCardinalityBehavior.NULL)
+           return null;
+       if (code == ActionCardinalityBehavior.SINGLE)
       return "single";
     if (code == ActionCardinalityBehavior.MULTIPLE)
       return "multiple";
     return "?";
-  }
+   }
 
   public String toSystem(ActionCardinalityBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionGroupingBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionGroupingBehaviorEnumFactory.java
index ada631107e..f58f54f1d0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionGroupingBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionGroupingBehaviorEnumFactory.java
@@ -48,14 +48,16 @@ public ActionGroupingBehavior fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ActionGroupingBehavior code) {
-    if (code == ActionGroupingBehavior.VISUALGROUP)
+       if (code == ActionGroupingBehavior.NULL)
+           return null;
+       if (code == ActionGroupingBehavior.VISUALGROUP)
       return "visual-group";
     if (code == ActionGroupingBehavior.LOGICALGROUP)
       return "logical-group";
     if (code == ActionGroupingBehavior.SENTENCEGROUP)
       return "sentence-group";
     return "?";
-  }
+   }
 
   public String toSystem(ActionGroupingBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionParticipantTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionParticipantTypeEnumFactory.java
index d3f5c7c808..4c2bf9454a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionParticipantTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionParticipantTypeEnumFactory.java
@@ -48,14 +48,16 @@ public ActionParticipantType fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ActionParticipantType code) {
-    if (code == ActionParticipantType.PATIENT)
+       if (code == ActionParticipantType.NULL)
+           return null;
+       if (code == ActionParticipantType.PATIENT)
       return "patient";
     if (code == ActionParticipantType.PRACTITIONER)
       return "practitioner";
     if (code == ActionParticipantType.RELATEDPERSON)
       return "related-person";
     return "?";
-  }
+   }
 
   public String toSystem(ActionParticipantType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionPrecheckBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionPrecheckBehaviorEnumFactory.java
index 4881009d1c..a9b4a48350 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionPrecheckBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionPrecheckBehaviorEnumFactory.java
@@ -46,12 +46,14 @@ public ActionPrecheckBehavior fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ActionPrecheckBehavior code) {
-    if (code == ActionPrecheckBehavior.YES)
+       if (code == ActionPrecheckBehavior.NULL)
+           return null;
+       if (code == ActionPrecheckBehavior.YES)
       return "yes";
     if (code == ActionPrecheckBehavior.NO)
       return "no";
     return "?";
-  }
+   }
 
   public String toSystem(ActionPrecheckBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipAnchorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipAnchorEnumFactory.java
index 9acabda64c..c842b379af 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipAnchorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipAnchorEnumFactory.java
@@ -46,12 +46,14 @@ public ActionRelationshipAnchor fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(ActionRelationshipAnchor code) {
-    if (code == ActionRelationshipAnchor.START)
+       if (code == ActionRelationshipAnchor.NULL)
+           return null;
+       if (code == ActionRelationshipAnchor.START)
       return "start";
     if (code == ActionRelationshipAnchor.END)
       return "end";
     return "?";
-  }
+   }
 
   public String toSystem(ActionRelationshipAnchor code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipTypeEnumFactory.java
index 98408ff6b0..0f2cfcdcf9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRelationshipTypeEnumFactory.java
@@ -46,12 +46,14 @@ public ActionRelationshipType fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ActionRelationshipType code) {
-    if (code == ActionRelationshipType.BEFORE)
+       if (code == ActionRelationshipType.NULL)
+           return null;
+       if (code == ActionRelationshipType.BEFORE)
       return "before";
     if (code == ActionRelationshipType.AFTER)
       return "after";
     return "?";
-  }
+   }
 
   public String toSystem(ActionRelationshipType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRequiredBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRequiredBehaviorEnumFactory.java
index aac111eefe..9148a400bb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRequiredBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionRequiredBehaviorEnumFactory.java
@@ -48,14 +48,16 @@ public ActionRequiredBehavior fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ActionRequiredBehavior code) {
-    if (code == ActionRequiredBehavior.MUST)
+       if (code == ActionRequiredBehavior.NULL)
+           return null;
+       if (code == ActionRequiredBehavior.MUST)
       return "must";
     if (code == ActionRequiredBehavior.COULD)
       return "could";
     if (code == ActionRequiredBehavior.MUSTUNLESSDOCUMENTED)
       return "must-unless-documented";
     return "?";
-  }
+   }
 
   public String toSystem(ActionRequiredBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionSelectionBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionSelectionBehaviorEnumFactory.java
index f62f744cd2..3e1a0505bc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionSelectionBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionSelectionBehaviorEnumFactory.java
@@ -54,7 +54,9 @@ public ActionSelectionBehavior fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ActionSelectionBehavior code) {
-    if (code == ActionSelectionBehavior.ANY)
+       if (code == ActionSelectionBehavior.NULL)
+           return null;
+       if (code == ActionSelectionBehavior.ANY)
       return "any";
     if (code == ActionSelectionBehavior.ALL)
       return "all";
@@ -67,7 +69,7 @@ public String toCode(ActionSelectionBehavior code) {
     if (code == ActionSelectionBehavior.ONEORMORE)
       return "one-or-more";
     return "?";
-  }
+   }
 
   public String toSystem(ActionSelectionBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionTypeEnumFactory.java
index bb6ff9d905..7a2cb7a2ce 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionTypeEnumFactory.java
@@ -50,7 +50,9 @@ public ActionType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ActionType code) {
-    if (code == ActionType.CREATE)
+       if (code == ActionType.NULL)
+           return null;
+       if (code == ActionType.CREATE)
       return "create";
     if (code == ActionType.UPDATE)
       return "update";
@@ -59,7 +61,7 @@ public String toCode(ActionType code) {
     if (code == ActionType.FIREEVENT)
       return "fire-event";
     return "?";
-  }
+   }
 
   public String toSystem(ActionType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionlistEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionlistEnumFactory.java
index b7fffd5bc4..8132fbd4a8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionlistEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActionlistEnumFactory.java
@@ -50,7 +50,9 @@ public Actionlist fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Actionlist code) {
-    if (code == Actionlist.CANCEL)
+       if (code == Actionlist.NULL)
+           return null;
+       if (code == Actionlist.CANCEL)
       return "cancel";
     if (code == Actionlist.POLL)
       return "poll";
@@ -59,7 +61,7 @@ public String toCode(Actionlist code) {
     if (code == Actionlist.STATUS)
       return "status";
     return "?";
-  }
+   }
 
   public String toSystem(Actionlist code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActivityDefinitionCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActivityDefinitionCategoryEnumFactory.java
index 113a573a47..0b28c0ad8b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActivityDefinitionCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ActivityDefinitionCategoryEnumFactory.java
@@ -56,7 +56,9 @@ public ActivityDefinitionCategory fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(ActivityDefinitionCategory code) {
-    if (code == ActivityDefinitionCategory.DIET)
+       if (code == ActivityDefinitionCategory.NULL)
+           return null;
+       if (code == ActivityDefinitionCategory.DIET)
       return "diet";
     if (code == ActivityDefinitionCategory.DRUG)
       return "drug";
@@ -71,7 +73,7 @@ public String toCode(ActivityDefinitionCategory code) {
     if (code == ActivityDefinitionCategory.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(ActivityDefinitionCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdditionalmaterialsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdditionalmaterialsEnumFactory.java
index c2e262f492..5f1d213555 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdditionalmaterialsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdditionalmaterialsEnumFactory.java
@@ -54,7 +54,9 @@ public Additionalmaterials fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(Additionalmaterials code) {
-    if (code == Additionalmaterials.XRAY)
+       if (code == Additionalmaterials.NULL)
+           return null;
+       if (code == Additionalmaterials.XRAY)
       return "xray";
     if (code == Additionalmaterials.IMAGE)
       return "image";
@@ -67,7 +69,7 @@ public String toCode(Additionalmaterials code) {
     if (code == Additionalmaterials.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(Additionalmaterials code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressTypeEnumFactory.java
index 313f63a418..8479552bc8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressTypeEnumFactory.java
@@ -48,14 +48,16 @@ public AddressType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(AddressType code) {
-    if (code == AddressType.POSTAL)
+       if (code == AddressType.NULL)
+           return null;
+       if (code == AddressType.POSTAL)
       return "postal";
     if (code == AddressType.PHYSICAL)
       return "physical";
     if (code == AddressType.BOTH)
       return "both";
     return "?";
-  }
+   }
 
   public String toSystem(AddressType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressUseEnumFactory.java
index d65b45a31e..8c1502b20a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AddressUseEnumFactory.java
@@ -50,7 +50,9 @@ public AddressUse fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(AddressUse code) {
-    if (code == AddressUse.HOME)
+       if (code == AddressUse.NULL)
+           return null;
+       if (code == AddressUse.HOME)
       return "home";
     if (code == AddressUse.WORK)
       return "work";
@@ -59,7 +61,7 @@ public String toCode(AddressUse code) {
     if (code == AddressUse.OLD)
       return "old";
     return "?";
-  }
+   }
 
   public String toSystem(AddressUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationEnumFactory.java
index 39068b2662..a34c1323d5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationEnumFactory.java
@@ -56,7 +56,9 @@ public Adjudication fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(Adjudication code) {
-    if (code == Adjudication.TOTAL)
+       if (code == Adjudication.NULL)
+           return null;
+       if (code == Adjudication.TOTAL)
       return "total";
     if (code == Adjudication.COPAY)
       return "copay";
@@ -71,7 +73,7 @@ public String toCode(Adjudication code) {
     if (code == Adjudication.BENEFIT)
       return "benefit";
     return "?";
-  }
+   }
 
   public String toSystem(Adjudication code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationErrorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationErrorEnumFactory.java
index 36695f629e..1640f2d59c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationErrorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationErrorEnumFactory.java
@@ -46,12 +46,14 @@ public AdjudicationError fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(AdjudicationError code) {
-    if (code == AdjudicationError.A001)
+       if (code == AdjudicationError.NULL)
+           return null;
+       if (code == AdjudicationError.A001)
       return "a001";
     if (code == AdjudicationError.A002)
       return "a002";
     return "?";
-  }
+   }
 
   public String toSystem(AdjudicationError code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationReasonEnumFactory.java
index bb3a02c24c..759d9c2b57 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdjudicationReasonEnumFactory.java
@@ -46,12 +46,14 @@ public AdjudicationReason fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(AdjudicationReason code) {
-    if (code == AdjudicationReason.AR001)
+       if (code == AdjudicationReason.NULL)
+           return null;
+       if (code == AdjudicationReason.AR001)
       return "ar001";
     if (code == AdjudicationReason.AR002)
       return "ar002";
     return "?";
-  }
+   }
 
   public String toSystem(AdjudicationReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdministrativeGenderEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdministrativeGenderEnumFactory.java
index ef0c00c83d..dfe8a29ea2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdministrativeGenderEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AdministrativeGenderEnumFactory.java
@@ -50,7 +50,9 @@ public AdministrativeGender fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(AdministrativeGender code) {
-    if (code == AdministrativeGender.MALE)
+       if (code == AdministrativeGender.NULL)
+           return null;
+       if (code == AdministrativeGender.MALE)
       return "male";
     if (code == AdministrativeGender.FEMALE)
       return "female";
@@ -59,7 +61,7 @@ public String toCode(AdministrativeGender code) {
     if (code == AdministrativeGender.UNKNOWN)
       return "unknown";
     return "?";
-  }
+   }
 
   public String toSystem(AdministrativeGender code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCategoryEnumFactory.java
index 2ea6e5c39d..7b8ac7f9ef 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCategoryEnumFactory.java
@@ -50,7 +50,9 @@ public AllergyIntoleranceCategory fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(AllergyIntoleranceCategory code) {
-    if (code == AllergyIntoleranceCategory.FOOD)
+       if (code == AllergyIntoleranceCategory.NULL)
+           return null;
+       if (code == AllergyIntoleranceCategory.FOOD)
       return "food";
     if (code == AllergyIntoleranceCategory.MEDICATION)
       return "medication";
@@ -59,7 +61,7 @@ public String toCode(AllergyIntoleranceCategory code) {
     if (code == AllergyIntoleranceCategory.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(AllergyIntoleranceCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCriticalityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCriticalityEnumFactory.java
index aac6b5f036..fd78b86330 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCriticalityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceCriticalityEnumFactory.java
@@ -48,14 +48,16 @@ public AllergyIntoleranceCriticality fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(AllergyIntoleranceCriticality code) {
-    if (code == AllergyIntoleranceCriticality.LOW)
+       if (code == AllergyIntoleranceCriticality.NULL)
+           return null;
+       if (code == AllergyIntoleranceCriticality.LOW)
       return "low";
     if (code == AllergyIntoleranceCriticality.HIGH)
       return "high";
     if (code == AllergyIntoleranceCriticality.UNABLETOASSESS)
       return "unable-to-assess";
     return "?";
-  }
+   }
 
   public String toSystem(AllergyIntoleranceCriticality code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceStatusEnumFactory.java
index 348cda88db..55fa1625cb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceStatusEnumFactory.java
@@ -56,7 +56,9 @@ public AllergyIntoleranceStatus fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(AllergyIntoleranceStatus code) {
-    if (code == AllergyIntoleranceStatus.ACTIVE)
+       if (code == AllergyIntoleranceStatus.NULL)
+           return null;
+       if (code == AllergyIntoleranceStatus.ACTIVE)
       return "active";
     if (code == AllergyIntoleranceStatus.UNCONFIRMED)
       return "unconfirmed";
@@ -71,7 +73,7 @@ public String toCode(AllergyIntoleranceStatus code) {
     if (code == AllergyIntoleranceStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(AllergyIntoleranceStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceTypeEnumFactory.java
index 74e29dc20c..bbb4fd3957 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AllergyIntoleranceTypeEnumFactory.java
@@ -46,12 +46,14 @@ public AllergyIntoleranceType fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(AllergyIntoleranceType code) {
-    if (code == AllergyIntoleranceType.ALLERGY)
+       if (code == AllergyIntoleranceType.NULL)
+           return null;
+       if (code == AllergyIntoleranceType.ALLERGY)
       return "allergy";
     if (code == AllergyIntoleranceType.INTOLERANCE)
       return "intolerance";
     return "?";
-  }
+   }
 
   public String toSystem(AllergyIntoleranceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalBreedsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalBreedsEnumFactory.java
index 563f0904e7..372596929f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalBreedsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalBreedsEnumFactory.java
@@ -50,7 +50,9 @@ public AnimalBreeds fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(AnimalBreeds code) {
-    if (code == AnimalBreeds.GSD)
+       if (code == AnimalBreeds.NULL)
+           return null;
+       if (code == AnimalBreeds.GSD)
       return "gsd";
     if (code == AnimalBreeds.IRT)
       return "irt";
@@ -59,7 +61,7 @@ public String toCode(AnimalBreeds code) {
     if (code == AnimalBreeds.GRET)
       return "gret";
     return "?";
-  }
+   }
 
   public String toSystem(AnimalBreeds code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalGenderstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalGenderstatusEnumFactory.java
index eb0a5e2c1a..7050e47205 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalGenderstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalGenderstatusEnumFactory.java
@@ -48,14 +48,16 @@ public AnimalGenderstatus fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(AnimalGenderstatus code) {
-    if (code == AnimalGenderstatus.NEUTERED)
+       if (code == AnimalGenderstatus.NULL)
+           return null;
+       if (code == AnimalGenderstatus.NEUTERED)
       return "neutered";
     if (code == AnimalGenderstatus.INTACT)
       return "intact";
     if (code == AnimalGenderstatus.UNKNOWN)
       return "unknown";
     return "?";
-  }
+   }
 
   public String toSystem(AnimalGenderstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalSpeciesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalSpeciesEnumFactory.java
index e8a537d360..8434dac87a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalSpeciesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnimalSpeciesEnumFactory.java
@@ -48,14 +48,16 @@ public AnimalSpecies fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(AnimalSpecies code) {
-    if (code == AnimalSpecies.CANISLF)
+       if (code == AnimalSpecies.NULL)
+           return null;
+       if (code == AnimalSpecies.CANISLF)
       return "canislf";
     if (code == AnimalSpecies.OVISA)
       return "ovisa";
     if (code == AnimalSpecies.SERINUSCD)
       return "serinuscd";
     return "?";
-  }
+   }
 
   public String toSystem(AnimalSpecies code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnzscoOccupationsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnzscoOccupationsEnumFactory.java
index 79ed8e672c..e022a2442a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnzscoOccupationsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AnzscoOccupationsEnumFactory.java
@@ -2694,7 +2694,9 @@ public AnzscoOccupations fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(AnzscoOccupations code) {
-    if (code == AnzscoOccupations._100000)
+       if (code == AnzscoOccupations.NULL)
+           return null;
+       if (code == AnzscoOccupations._100000)
       return "100000";
     if (code == AnzscoOccupations._111000)
       return "111000";
@@ -5347,7 +5349,7 @@ public String toCode(AnzscoOccupations code) {
     if (code == AnzscoOccupations._899999)
       return "899999";
     return "?";
-  }
+   }
 
   public String toSystem(AnzscoOccupations code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AppointmentstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AppointmentstatusEnumFactory.java
index 129b0533bf..15563725b9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AppointmentstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AppointmentstatusEnumFactory.java
@@ -56,7 +56,9 @@ public Appointmentstatus fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(Appointmentstatus code) {
-    if (code == Appointmentstatus.PROPOSED)
+       if (code == Appointmentstatus.NULL)
+           return null;
+       if (code == Appointmentstatus.PROPOSED)
       return "proposed";
     if (code == Appointmentstatus.PENDING)
       return "pending";
@@ -71,7 +73,7 @@ public String toCode(Appointmentstatus code) {
     if (code == Appointmentstatus.NOSHOW)
       return "noshow";
     return "?";
-  }
+   }
 
   public String toSystem(Appointmentstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertDirectionCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertDirectionCodesEnumFactory.java
index 7284c49f72..4839c66eb2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertDirectionCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertDirectionCodesEnumFactory.java
@@ -46,12 +46,14 @@ public AssertDirectionCodes fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(AssertDirectionCodes code) {
-    if (code == AssertDirectionCodes.RESPONSE)
+       if (code == AssertDirectionCodes.NULL)
+           return null;
+       if (code == AssertDirectionCodes.RESPONSE)
       return "response";
     if (code == AssertDirectionCodes.REQUEST)
       return "request";
     return "?";
-  }
+   }
 
   public String toSystem(AssertDirectionCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertOperatorCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertOperatorCodesEnumFactory.java
index 8da97e34e9..f60f1c823a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertOperatorCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertOperatorCodesEnumFactory.java
@@ -62,7 +62,9 @@ public AssertOperatorCodes fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(AssertOperatorCodes code) {
-    if (code == AssertOperatorCodes.EQUALS)
+       if (code == AssertOperatorCodes.NULL)
+           return null;
+       if (code == AssertOperatorCodes.EQUALS)
       return "equals";
     if (code == AssertOperatorCodes.NOTEQUALS)
       return "notEquals";
@@ -83,7 +85,7 @@ public String toCode(AssertOperatorCodes code) {
     if (code == AssertOperatorCodes.NOTCONTAINS)
       return "notContains";
     return "?";
-  }
+   }
 
   public String toSystem(AssertOperatorCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertResponseCodeTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertResponseCodeTypesEnumFactory.java
index 90b8099fcb..a37a5cd81a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertResponseCodeTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AssertResponseCodeTypesEnumFactory.java
@@ -66,7 +66,9 @@ public AssertResponseCodeTypes fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(AssertResponseCodeTypes code) {
-    if (code == AssertResponseCodeTypes.OKAY)
+       if (code == AssertResponseCodeTypes.NULL)
+           return null;
+       if (code == AssertResponseCodeTypes.OKAY)
       return "okay";
     if (code == AssertResponseCodeTypes.CREATED)
       return "created";
@@ -91,7 +93,7 @@ public String toCode(AssertResponseCodeTypes code) {
     if (code == AssertResponseCodeTypes.UNPROCESSABLE)
       return "unprocessable";
     return "?";
-  }
+   }
 
   public String toSystem(AssertResponseCodeTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventActionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventActionEnumFactory.java
index 8d60d67a98..b8d91d8ddc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventActionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventActionEnumFactory.java
@@ -52,7 +52,9 @@ public AuditEventAction fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(AuditEventAction code) {
-    if (code == AuditEventAction.C)
+       if (code == AuditEventAction.NULL)
+           return null;
+       if (code == AuditEventAction.C)
       return "C";
     if (code == AuditEventAction.R)
       return "R";
@@ -63,7 +65,7 @@ public String toCode(AuditEventAction code) {
     if (code == AuditEventAction.E)
       return "E";
     return "?";
-  }
+   }
 
   public String toSystem(AuditEventAction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventOutcomeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventOutcomeEnumFactory.java
index f080f3a75e..af387652cf 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventOutcomeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventOutcomeEnumFactory.java
@@ -50,7 +50,9 @@ public AuditEventOutcome fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(AuditEventOutcome code) {
-    if (code == AuditEventOutcome._0)
+       if (code == AuditEventOutcome.NULL)
+           return null;
+       if (code == AuditEventOutcome._0)
       return "0";
     if (code == AuditEventOutcome._4)
       return "4";
@@ -59,7 +61,7 @@ public String toCode(AuditEventOutcome code) {
     if (code == AuditEventOutcome._12)
       return "12";
     return "?";
-  }
+   }
 
   public String toSystem(AuditEventOutcome code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventTypeEnumFactory.java
index 71a152357c..e6009dbd10 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditEventTypeEnumFactory.java
@@ -44,10 +44,12 @@ public AuditEventType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(AuditEventType code) {
-    if (code == AuditEventType.REST)
+       if (code == AuditEventType.NULL)
+           return null;
+       if (code == AuditEventType.REST)
       return "rest";
     return "?";
-  }
+   }
 
   public String toSystem(AuditEventType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditSourceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditSourceTypeEnumFactory.java
index 744f558acc..e6c8f33f33 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditSourceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/AuditSourceTypeEnumFactory.java
@@ -60,7 +60,9 @@ public AuditSourceType fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(AuditSourceType code) {
-    if (code == AuditSourceType._1)
+       if (code == AuditSourceType.NULL)
+           return null;
+       if (code == AuditSourceType._1)
       return "1";
     if (code == AuditSourceType._2)
       return "2";
@@ -79,7 +81,7 @@ public String toCode(AuditSourceType code) {
     if (code == AuditSourceType._9)
       return "9";
     return "?";
-  }
+   }
 
   public String toSystem(AuditSourceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BasicResourceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BasicResourceTypeEnumFactory.java
index c6bb18c852..d866fb6434 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BasicResourceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BasicResourceTypeEnumFactory.java
@@ -74,7 +74,9 @@ public BasicResourceType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(BasicResourceType code) {
-    if (code == BasicResourceType.CONSENT)
+       if (code == BasicResourceType.NULL)
+           return null;
+       if (code == BasicResourceType.CONSENT)
       return "consent";
     if (code == BasicResourceType.REFERRAL)
       return "referral";
@@ -107,7 +109,7 @@ public String toCode(BasicResourceType code) {
     if (code == BasicResourceType.PROTOCOL)
       return "protocol";
     return "?";
-  }
+   }
 
   public String toSystem(BasicResourceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitCategoryEnumFactory.java
index edb7414b5b..8ee2c1e461 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitCategoryEnumFactory.java
@@ -50,7 +50,9 @@ public BenefitCategory fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(BenefitCategory code) {
-    if (code == BenefitCategory.ORAL)
+       if (code == BenefitCategory.NULL)
+           return null;
+       if (code == BenefitCategory.ORAL)
       return "oral";
     if (code == BenefitCategory.VISION)
       return "vision";
@@ -59,7 +61,7 @@ public String toCode(BenefitCategory code) {
     if (code == BenefitCategory.PHARMACY)
       return "pharmacy";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitNetworkEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitNetworkEnumFactory.java
index 749e483e5a..1f4cb78f1b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitNetworkEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitNetworkEnumFactory.java
@@ -46,12 +46,14 @@ public BenefitNetwork fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(BenefitNetwork code) {
-    if (code == BenefitNetwork.IN)
+       if (code == BenefitNetwork.NULL)
+           return null;
+       if (code == BenefitNetwork.IN)
       return "in";
     if (code == BenefitNetwork.OUT)
       return "out";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitNetwork code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitSubcategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitSubcategoryEnumFactory.java
index e441bbcce1..c04bac7ce0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitSubcategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitSubcategoryEnumFactory.java
@@ -58,7 +58,9 @@ public BenefitSubcategory fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(BenefitSubcategory code) {
-    if (code == BenefitSubcategory.ORALBASIC)
+       if (code == BenefitSubcategory.NULL)
+           return null;
+       if (code == BenefitSubcategory.ORALBASIC)
       return "oral-basic";
     if (code == BenefitSubcategory.ORALMAJOR)
       return "oral-major";
@@ -75,7 +77,7 @@ public String toCode(BenefitSubcategory code) {
     if (code == BenefitSubcategory.PHARMACYDISPENSE)
       return "pharmacy-dispense";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitSubcategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTermEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTermEnumFactory.java
index 0f72a15be2..548a0edf80 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTermEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTermEnumFactory.java
@@ -46,12 +46,14 @@ public BenefitTerm fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(BenefitTerm code) {
-    if (code == BenefitTerm.ANNUAL)
+       if (code == BenefitTerm.NULL)
+           return null;
+       if (code == BenefitTerm.ANNUAL)
       return "annual";
     if (code == BenefitTerm.LIFETIME)
       return "lifetime";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitTerm code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTypeEnumFactory.java
index e7848980e5..0d318c3c5f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitTypeEnumFactory.java
@@ -58,7 +58,9 @@ public BenefitType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(BenefitType code) {
-    if (code == BenefitType.DEDUCTABLE)
+       if (code == BenefitType.NULL)
+           return null;
+       if (code == BenefitType.DEDUCTABLE)
       return "deductable";
     if (code == BenefitType.VISIT)
       return "visit";
@@ -75,7 +77,7 @@ public String toCode(BenefitType code) {
     if (code == BenefitType.PHARMACYDISPENSE)
       return "pharmacy-dispense";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitUnitEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitUnitEnumFactory.java
index 6662a5db8c..685c4f321d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitUnitEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BenefitUnitEnumFactory.java
@@ -46,12 +46,14 @@ public BenefitUnit fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(BenefitUnit code) {
-    if (code == BenefitUnit.INDIVIDUAL)
+       if (code == BenefitUnit.NULL)
+           return null;
+       if (code == BenefitUnit.INDIVIDUAL)
       return "individual";
     if (code == BenefitUnit.FAMILY)
       return "family";
     return "?";
-  }
+   }
 
   public String toSystem(BenefitUnit code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BindingStrengthEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BindingStrengthEnumFactory.java
index 6d4ebd205a..527650bafd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BindingStrengthEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BindingStrengthEnumFactory.java
@@ -50,7 +50,9 @@ public BindingStrength fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(BindingStrength code) {
-    if (code == BindingStrength.REQUIRED)
+       if (code == BindingStrength.NULL)
+           return null;
+       if (code == BindingStrength.REQUIRED)
       return "required";
     if (code == BindingStrength.EXTENSIBLE)
       return "extensible";
@@ -59,7 +61,7 @@ public String toCode(BindingStrength code) {
     if (code == BindingStrength.EXAMPLE)
       return "example";
     return "?";
-  }
+   }
 
   public String toSystem(BindingStrength code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BundleTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BundleTypeEnumFactory.java
index 77add6c7a9..3b4079143e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BundleTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/BundleTypeEnumFactory.java
@@ -60,7 +60,9 @@ public BundleType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(BundleType code) {
-    if (code == BundleType.DOCUMENT)
+       if (code == BundleType.NULL)
+           return null;
+       if (code == BundleType.DOCUMENT)
       return "document";
     if (code == BundleType.MESSAGE)
       return "message";
@@ -79,7 +81,7 @@ public String toCode(BundleType code) {
     if (code == BundleType.COLLECTION)
       return "collection";
     return "?";
-  }
+   }
 
   public String toSystem(BundleType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CardinalityBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CardinalityBehaviorEnumFactory.java
index 7ce0428475..7feb54750e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CardinalityBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CardinalityBehaviorEnumFactory.java
@@ -46,12 +46,14 @@ public CardinalityBehavior fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(CardinalityBehavior code) {
-    if (code == CardinalityBehavior.SINGLE)
+       if (code == CardinalityBehavior.NULL)
+           return null;
+       if (code == CardinalityBehavior.SINGLE)
       return "single";
     if (code == CardinalityBehavior.MULTIPLE)
       return "multiple";
     return "?";
-  }
+   }
 
   public String toSystem(CardinalityBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityCategoryEnumFactory.java
index 79d17f826f..b191a36f39 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityCategoryEnumFactory.java
@@ -56,7 +56,9 @@ public CarePlanActivityCategory fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(CarePlanActivityCategory code) {
-    if (code == CarePlanActivityCategory.DIET)
+       if (code == CarePlanActivityCategory.NULL)
+           return null;
+       if (code == CarePlanActivityCategory.DIET)
       return "diet";
     if (code == CarePlanActivityCategory.DRUG)
       return "drug";
@@ -71,7 +73,7 @@ public String toCode(CarePlanActivityCategory code) {
     if (code == CarePlanActivityCategory.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(CarePlanActivityCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityStatusEnumFactory.java
index 1b805b0f74..096c19c8cc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanActivityStatusEnumFactory.java
@@ -54,7 +54,9 @@ public CarePlanActivityStatus fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(CarePlanActivityStatus code) {
-    if (code == CarePlanActivityStatus.NOTSTARTED)
+       if (code == CarePlanActivityStatus.NULL)
+           return null;
+       if (code == CarePlanActivityStatus.NOTSTARTED)
       return "not-started";
     if (code == CarePlanActivityStatus.SCHEDULED)
       return "scheduled";
@@ -67,7 +69,7 @@ public String toCode(CarePlanActivityStatus code) {
     if (code == CarePlanActivityStatus.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(CarePlanActivityStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanRelationshipEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanRelationshipEnumFactory.java
index 0ed69b944d..df282ea415 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanRelationshipEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanRelationshipEnumFactory.java
@@ -48,14 +48,16 @@ public CarePlanRelationship fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(CarePlanRelationship code) {
-    if (code == CarePlanRelationship.INCLUDES)
+       if (code == CarePlanRelationship.NULL)
+           return null;
+       if (code == CarePlanRelationship.INCLUDES)
       return "includes";
     if (code == CarePlanRelationship.REPLACES)
       return "replaces";
     if (code == CarePlanRelationship.FULFILLS)
       return "fulfills";
     return "?";
-  }
+   }
 
   public String toSystem(CarePlanRelationship code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanStatusEnumFactory.java
index 7c4aa59193..c29d160ae3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CarePlanStatusEnumFactory.java
@@ -52,7 +52,9 @@ public CarePlanStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(CarePlanStatus code) {
-    if (code == CarePlanStatus.PROPOSED)
+       if (code == CarePlanStatus.NULL)
+           return null;
+       if (code == CarePlanStatus.PROPOSED)
       return "proposed";
     if (code == CarePlanStatus.DRAFT)
       return "draft";
@@ -63,7 +65,7 @@ public String toCode(CarePlanStatus code) {
     if (code == CarePlanStatus.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(CarePlanStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleActionTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleActionTypeEnumFactory.java
index 0c08eed3d0..d42f7060e3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleActionTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleActionTypeEnumFactory.java
@@ -50,7 +50,9 @@ public CdsRuleActionType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(CdsRuleActionType code) {
-    if (code == CdsRuleActionType.CREATE)
+       if (code == CdsRuleActionType.NULL)
+           return null;
+       if (code == CdsRuleActionType.CREATE)
       return "create";
     if (code == CdsRuleActionType.UPDATE)
       return "update";
@@ -59,7 +61,7 @@ public String toCode(CdsRuleActionType code) {
     if (code == CdsRuleActionType.FIREEVENT)
       return "fire-event";
     return "?";
-  }
+   }
 
   public String toSystem(CdsRuleActionType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleParticipantEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleParticipantEnumFactory.java
index 989af8707f..4bf160c81f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleParticipantEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleParticipantEnumFactory.java
@@ -50,7 +50,9 @@ public CdsRuleParticipant fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(CdsRuleParticipant code) {
-    if (code == CdsRuleParticipant.PATIENT)
+       if (code == CdsRuleParticipant.NULL)
+           return null;
+       if (code == CdsRuleParticipant.PATIENT)
       return "patient";
     if (code == CdsRuleParticipant.PERSON)
       return "person";
@@ -59,7 +61,7 @@ public String toCode(CdsRuleParticipant code) {
     if (code == CdsRuleParticipant.RELATEDPERSON)
       return "related-person";
     return "?";
-  }
+   }
 
   public String toSystem(CdsRuleParticipant code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleTriggerTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleTriggerTypeEnumFactory.java
index cf16a5d65c..fc395bc9c4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleTriggerTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CdsRuleTriggerTypeEnumFactory.java
@@ -56,7 +56,9 @@ public CdsRuleTriggerType fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(CdsRuleTriggerType code) {
-    if (code == CdsRuleTriggerType.NAMEDEVENT)
+       if (code == CdsRuleTriggerType.NULL)
+           return null;
+       if (code == CdsRuleTriggerType.NAMEDEVENT)
       return "named-event";
     if (code == CdsRuleTriggerType.PERIODIC)
       return "periodic";
@@ -71,7 +73,7 @@ public String toCode(CdsRuleTriggerType code) {
     if (code == CdsRuleTriggerType.DATAACCESSENDED)
       return "data-access-ended";
     return "?";
-  }
+   }
 
   public String toSystem(CdsRuleTriggerType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChoiceListOrientationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChoiceListOrientationEnumFactory.java
index 2c37ee3ce4..661cc3072a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChoiceListOrientationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChoiceListOrientationEnumFactory.java
@@ -46,12 +46,14 @@ public ChoiceListOrientation fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ChoiceListOrientation code) {
-    if (code == ChoiceListOrientation.HORIZONTAL)
+       if (code == ChoiceListOrientation.NULL)
+           return null;
+       if (code == ChoiceListOrientation.HORIZONTAL)
       return "horizontal";
     if (code == ChoiceListOrientation.VERTICAL)
       return "vertical";
     return "?";
-  }
+   }
 
   public String toSystem(ChoiceListOrientation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChromosomeHumanEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChromosomeHumanEnumFactory.java
index 6d0ef5c9d4..ceb3791b7b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChromosomeHumanEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ChromosomeHumanEnumFactory.java
@@ -90,7 +90,9 @@ public ChromosomeHuman fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ChromosomeHuman code) {
-    if (code == ChromosomeHuman._1)
+       if (code == ChromosomeHuman.NULL)
+           return null;
+       if (code == ChromosomeHuman._1)
       return "1";
     if (code == ChromosomeHuman._2)
       return "2";
@@ -139,7 +141,7 @@ public String toCode(ChromosomeHuman code) {
     if (code == ChromosomeHuman.Y)
       return "Y";
     return "?";
-  }
+   }
 
   public String toSystem(ChromosomeHuman code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimExceptionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimExceptionEnumFactory.java
index 95a46e228d..4162e16758 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimExceptionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimExceptionEnumFactory.java
@@ -46,12 +46,14 @@ public ClaimException fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ClaimException code) {
-    if (code == ClaimException.STUDENT)
+       if (code == ClaimException.NULL)
+           return null;
+       if (code == ClaimException.STUDENT)
       return "student";
     if (code == ClaimException.DISABLED)
       return "disabled";
     return "?";
-  }
+   }
 
   public String toSystem(ClaimException code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimModifiersEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimModifiersEnumFactory.java
index 8991f48b2e..37f9adc390 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimModifiersEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimModifiersEnumFactory.java
@@ -52,7 +52,9 @@ public ClaimModifiers fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ClaimModifiers code) {
-    if (code == ClaimModifiers.A)
+       if (code == ClaimModifiers.NULL)
+           return null;
+       if (code == ClaimModifiers.A)
       return "A";
     if (code == ClaimModifiers.B)
       return "B";
@@ -63,7 +65,7 @@ public String toCode(ClaimModifiers code) {
     if (code == ClaimModifiers.X)
       return "X";
     return "?";
-  }
+   }
 
   public String toSystem(ClaimModifiers code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimSubtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimSubtypeEnumFactory.java
index 0346965817..2f6420efdb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimSubtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimSubtypeEnumFactory.java
@@ -46,12 +46,14 @@ public ClaimSubtype fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ClaimSubtype code) {
-    if (code == ClaimSubtype.ORTHO)
+       if (code == ClaimSubtype.NULL)
+           return null;
+       if (code == ClaimSubtype.ORTHO)
       return "ortho";
     if (code == ClaimSubtype.EMERGENCY)
       return "emergency";
     return "?";
-  }
+   }
 
   public String toSystem(ClaimSubtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimTypeLinkEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimTypeLinkEnumFactory.java
index 8f0ecb8194..68f989eb54 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimTypeLinkEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimTypeLinkEnumFactory.java
@@ -52,7 +52,9 @@ public ClaimTypeLink fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ClaimTypeLink code) {
-    if (code == ClaimTypeLink.INSTITUTIONAL)
+       if (code == ClaimTypeLink.NULL)
+           return null;
+       if (code == ClaimTypeLink.INSTITUTIONAL)
       return "institutional";
     if (code == ClaimTypeLink.ORAL)
       return "oral";
@@ -63,7 +65,7 @@ public String toCode(ClaimTypeLink code) {
     if (code == ClaimTypeLink.VISION)
       return "vision";
     return "?";
-  }
+   }
 
   public String toSystem(ClaimTypeLink code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimUseLinkEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimUseLinkEnumFactory.java
index bd92ab9947..97309f6db0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimUseLinkEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClaimUseLinkEnumFactory.java
@@ -50,7 +50,9 @@ public ClaimUseLink fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ClaimUseLink code) {
-    if (code == ClaimUseLink.COMPLETE)
+       if (code == ClaimUseLink.NULL)
+           return null;
+       if (code == ClaimUseLink.COMPLETE)
       return "complete";
     if (code == ClaimUseLink.PROPOSED)
       return "proposed";
@@ -59,7 +61,7 @@ public String toCode(ClaimUseLink code) {
     if (code == ClaimUseLink.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(ClaimUseLink code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClassificationOrContextEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClassificationOrContextEnumFactory.java
index 0d1f99fb31..64cd13cc8e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClassificationOrContextEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClassificationOrContextEnumFactory.java
@@ -46,12 +46,14 @@ public ClassificationOrContext fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ClassificationOrContext code) {
-    if (code == ClassificationOrContext.CLASSIFICATION)
+       if (code == ClassificationOrContext.NULL)
+           return null;
+       if (code == ClassificationOrContext.CLASSIFICATION)
       return "classification";
     if (code == ClassificationOrContext.CONTEXT)
       return "context";
     return "?";
-  }
+   }
 
   public String toSystem(ClassificationOrContext code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClinicalImpressionStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClinicalImpressionStatusEnumFactory.java
index 1d9eeb4e8a..5f0b9473ae 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClinicalImpressionStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ClinicalImpressionStatusEnumFactory.java
@@ -48,14 +48,16 @@ public ClinicalImpressionStatus fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(ClinicalImpressionStatus code) {
-    if (code == ClinicalImpressionStatus.INPROGRESS)
+       if (code == ClinicalImpressionStatus.NULL)
+           return null;
+       if (code == ClinicalImpressionStatus.INPROGRESS)
       return "in-progress";
     if (code == ClinicalImpressionStatus.COMPLETED)
       return "completed";
     if (code == ClinicalImpressionStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(ClinicalImpressionStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CodesystemContentModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CodesystemContentModeEnumFactory.java
index a882cb805f..c251a24c69 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CodesystemContentModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CodesystemContentModeEnumFactory.java
@@ -50,7 +50,9 @@ public CodesystemContentMode fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(CodesystemContentMode code) {
-    if (code == CodesystemContentMode.NOTPRESENT)
+       if (code == CodesystemContentMode.NULL)
+           return null;
+       if (code == CodesystemContentMode.NOTPRESENT)
       return "not-present";
     if (code == CodesystemContentMode.EXAMPLAR)
       return "examplar";
@@ -59,7 +61,7 @@ public String toCode(CodesystemContentMode code) {
     if (code == CodesystemContentMode.COMPLETE)
       return "complete";
     return "?";
-  }
+   }
 
   public String toSystem(CodesystemContentMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationRequestStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationRequestStatusEnumFactory.java
index 84a3f54bce..ab2ddee6f8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationRequestStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationRequestStatusEnumFactory.java
@@ -62,7 +62,9 @@ public CommunicationRequestStatus fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(CommunicationRequestStatus code) {
-    if (code == CommunicationRequestStatus.PROPOSED)
+       if (code == CommunicationRequestStatus.NULL)
+           return null;
+       if (code == CommunicationRequestStatus.PROPOSED)
       return "proposed";
     if (code == CommunicationRequestStatus.PLANNED)
       return "planned";
@@ -83,7 +85,7 @@ public String toCode(CommunicationRequestStatus code) {
     if (code == CommunicationRequestStatus.FAILED)
       return "failed";
     return "?";
-  }
+   }
 
   public String toSystem(CommunicationRequestStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationStatusEnumFactory.java
index f42263157e..a23541e61d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CommunicationStatusEnumFactory.java
@@ -52,7 +52,9 @@ public CommunicationStatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(CommunicationStatus code) {
-    if (code == CommunicationStatus.INPROGRESS)
+       if (code == CommunicationStatus.NULL)
+           return null;
+       if (code == CommunicationStatus.INPROGRESS)
       return "in-progress";
     if (code == CommunicationStatus.COMPLETED)
       return "completed";
@@ -63,7 +65,7 @@ public String toCode(CommunicationStatus code) {
     if (code == CommunicationStatus.FAILED)
       return "failed";
     return "?";
-  }
+   }
 
   public String toSystem(CommunicationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompartmentTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompartmentTypeEnumFactory.java
index 9adb23b3ec..5c944ca7ad 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompartmentTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompartmentTypeEnumFactory.java
@@ -52,7 +52,9 @@ public CompartmentType fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(CompartmentType code) {
-    if (code == CompartmentType.PATIENT)
+       if (code == CompartmentType.NULL)
+           return null;
+       if (code == CompartmentType.PATIENT)
       return "Patient";
     if (code == CompartmentType.ENCOUNTER)
       return "Encounter";
@@ -63,7 +65,7 @@ public String toCode(CompartmentType code) {
     if (code == CompartmentType.DEVICE)
       return "Device";
     return "?";
-  }
+   }
 
   public String toSystem(CompartmentType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionAttestationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionAttestationModeEnumFactory.java
index e333a3c26f..2a08c64451 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionAttestationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionAttestationModeEnumFactory.java
@@ -50,7 +50,9 @@ public CompositionAttestationMode fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(CompositionAttestationMode code) {
-    if (code == CompositionAttestationMode.PERSONAL)
+       if (code == CompositionAttestationMode.NULL)
+           return null;
+       if (code == CompositionAttestationMode.PERSONAL)
       return "personal";
     if (code == CompositionAttestationMode.PROFESSIONAL)
       return "professional";
@@ -59,7 +61,7 @@ public String toCode(CompositionAttestationMode code) {
     if (code == CompositionAttestationMode.OFFICIAL)
       return "official";
     return "?";
-  }
+   }
 
   public String toSystem(CompositionAttestationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionStatusEnumFactory.java
index 74af590c31..e74df4c8c2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CompositionStatusEnumFactory.java
@@ -50,7 +50,9 @@ public CompositionStatus fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(CompositionStatus code) {
-    if (code == CompositionStatus.PRELIMINARY)
+       if (code == CompositionStatus.NULL)
+           return null;
+       if (code == CompositionStatus.PRELIMINARY)
       return "preliminary";
     if (code == CompositionStatus.FINAL)
       return "final";
@@ -59,7 +61,7 @@ public String toCode(CompositionStatus code) {
     if (code == CompositionStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(CompositionStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptMapEquivalenceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptMapEquivalenceEnumFactory.java
index b0b99c2207..e15cd889a5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptMapEquivalenceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptMapEquivalenceEnumFactory.java
@@ -60,7 +60,9 @@ public ConceptMapEquivalence fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ConceptMapEquivalence code) {
-    if (code == ConceptMapEquivalence.EQUIVALENT)
+       if (code == ConceptMapEquivalence.NULL)
+           return null;
+       if (code == ConceptMapEquivalence.EQUIVALENT)
       return "equivalent";
     if (code == ConceptMapEquivalence.EQUAL)
       return "equal";
@@ -79,7 +81,7 @@ public String toCode(ConceptMapEquivalence code) {
     if (code == ConceptMapEquivalence.DISJOINT)
       return "disjoint";
     return "?";
-  }
+   }
 
   public String toSystem(ConceptMapEquivalence code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptPropertyTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptPropertyTypeEnumFactory.java
index 75511d5d28..6a79face54 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptPropertyTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConceptPropertyTypeEnumFactory.java
@@ -54,7 +54,9 @@ public ConceptPropertyType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(ConceptPropertyType code) {
-    if (code == ConceptPropertyType.CODE)
+       if (code == ConceptPropertyType.NULL)
+           return null;
+       if (code == ConceptPropertyType.CODE)
       return "code";
     if (code == ConceptPropertyType.CODING)
       return "Coding";
@@ -67,7 +69,7 @@ public String toCode(ConceptPropertyType code) {
     if (code == ConceptPropertyType.DATETIME)
       return "dateTime";
     return "?";
-  }
+   }
 
   public String toSystem(ConceptPropertyType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionCategoryEnumFactory.java
index 2dbe343bd8..003fe21c30 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionCategoryEnumFactory.java
@@ -50,7 +50,9 @@ public ConditionCategory fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(ConditionCategory code) {
-    if (code == ConditionCategory.COMPLAINT)
+       if (code == ConditionCategory.NULL)
+           return null;
+       if (code == ConditionCategory.COMPLAINT)
       return "complaint";
     if (code == ConditionCategory.SYMPTOM)
       return "symptom";
@@ -59,7 +61,7 @@ public String toCode(ConditionCategory code) {
     if (code == ConditionCategory.DIAGNOSIS)
       return "diagnosis";
     return "?";
-  }
+   }
 
   public String toSystem(ConditionCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionClinicalEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionClinicalEnumFactory.java
index 48e74e432a..c57dc7197e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionClinicalEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionClinicalEnumFactory.java
@@ -50,7 +50,9 @@ public ConditionClinical fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(ConditionClinical code) {
-    if (code == ConditionClinical.ACTIVE)
+       if (code == ConditionClinical.NULL)
+           return null;
+       if (code == ConditionClinical.ACTIVE)
       return "active";
     if (code == ConditionClinical.RELAPSE)
       return "relapse";
@@ -59,7 +61,7 @@ public String toCode(ConditionClinical code) {
     if (code == ConditionClinical.RESOLVED)
       return "resolved";
     return "?";
-  }
+   }
 
   public String toSystem(ConditionClinical code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionStateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionStateEnumFactory.java
index f4d040759f..bb0819a785 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionStateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionStateEnumFactory.java
@@ -48,14 +48,16 @@ public ConditionState fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ConditionState code) {
-    if (code == ConditionState.ACTIVE)
+       if (code == ConditionState.NULL)
+           return null;
+       if (code == ConditionState.ACTIVE)
       return "active";
     if (code == ConditionState.INACTIVE)
       return "inactive";
     if (code == ConditionState.RESOLVED)
       return "resolved";
     return "?";
-  }
+   }
 
   public String toSystem(ConditionState code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionVerStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionVerStatusEnumFactory.java
index d40f683efc..eccd5a6522 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionVerStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionVerStatusEnumFactory.java
@@ -54,7 +54,9 @@ public ConditionVerStatus fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ConditionVerStatus code) {
-    if (code == ConditionVerStatus.PROVISIONAL)
+       if (code == ConditionVerStatus.NULL)
+           return null;
+       if (code == ConditionVerStatus.PROVISIONAL)
       return "provisional";
     if (code == ConditionVerStatus.DIFFERENTIAL)
       return "differential";
@@ -67,7 +69,7 @@ public String toCode(ConditionVerStatus code) {
     if (code == ConditionVerStatus.UNKNOWN)
       return "unknown";
     return "?";
-  }
+   }
 
   public String toSystem(ConditionVerStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionalDeleteStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionalDeleteStatusEnumFactory.java
index 1d1e77b804..b5189d528b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionalDeleteStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConditionalDeleteStatusEnumFactory.java
@@ -48,14 +48,16 @@ public ConditionalDeleteStatus fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ConditionalDeleteStatus code) {
-    if (code == ConditionalDeleteStatus.NOTSUPPORTED)
+       if (code == ConditionalDeleteStatus.NULL)
+           return null;
+       if (code == ConditionalDeleteStatus.NOTSUPPORTED)
       return "not-supported";
     if (code == ConditionalDeleteStatus.SINGLE)
       return "single";
     if (code == ConditionalDeleteStatus.MULTIPLE)
       return "multiple";
     return "?";
-  }
+   }
 
   public String toSystem(ConditionalDeleteStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceExpectationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceExpectationEnumFactory.java
index 0130032356..88077d52c8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceExpectationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceExpectationEnumFactory.java
@@ -50,7 +50,9 @@ public ConformanceExpectation fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ConformanceExpectation code) {
-    if (code == ConformanceExpectation.SHALL)
+       if (code == ConformanceExpectation.NULL)
+           return null;
+       if (code == ConformanceExpectation.SHALL)
       return "SHALL";
     if (code == ConformanceExpectation.SHOULD)
       return "SHOULD";
@@ -59,7 +61,7 @@ public String toCode(ConformanceExpectation code) {
     if (code == ConformanceExpectation.SHOULDNOT)
       return "SHOULD-NOT";
     return "?";
-  }
+   }
 
   public String toSystem(ConformanceExpectation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceResourceStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceResourceStatusEnumFactory.java
index 487bac6531..43177687f2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceResourceStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceResourceStatusEnumFactory.java
@@ -48,14 +48,16 @@ public ConformanceResourceStatus fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(ConformanceResourceStatus code) {
-    if (code == ConformanceResourceStatus.DRAFT)
+       if (code == ConformanceResourceStatus.NULL)
+           return null;
+       if (code == ConformanceResourceStatus.DRAFT)
       return "draft";
     if (code == ConformanceResourceStatus.ACTIVE)
       return "active";
     if (code == ConformanceResourceStatus.RETIRED)
       return "retired";
     return "?";
-  }
+   }
 
   public String toSystem(ConformanceResourceStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceStatementKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceStatementKindEnumFactory.java
index 90b6e4b074..2de469f827 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceStatementKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConformanceStatementKindEnumFactory.java
@@ -48,14 +48,16 @@ public ConformanceStatementKind fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(ConformanceStatementKind code) {
-    if (code == ConformanceStatementKind.INSTANCE)
+       if (code == ConformanceStatementKind.NULL)
+           return null;
+       if (code == ConformanceStatementKind.INSTANCE)
       return "instance";
     if (code == ConformanceStatementKind.CAPABILITY)
       return "capability";
     if (code == ConformanceStatementKind.REQUIREMENTS)
       return "requirements";
     return "?";
-  }
+   }
 
   public String toSystem(ConformanceStatementKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConstraintSeverityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConstraintSeverityEnumFactory.java
index 847fdc423e..4bdcf05fe8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConstraintSeverityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ConstraintSeverityEnumFactory.java
@@ -46,12 +46,14 @@ public ConstraintSeverity fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ConstraintSeverity code) {
-    if (code == ConstraintSeverity.ERROR)
+       if (code == ConstraintSeverity.NULL)
+           return null;
+       if (code == ConstraintSeverity.ERROR)
       return "error";
     if (code == ConstraintSeverity.WARNING)
       return "warning";
     return "?";
-  }
+   }
 
   public String toSystem(ConstraintSeverity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointSystemEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointSystemEnumFactory.java
index c112b4a9b8..29ae74fcfd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointSystemEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointSystemEnumFactory.java
@@ -52,7 +52,9 @@ public ContactPointSystem fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ContactPointSystem code) {
-    if (code == ContactPointSystem.PHONE)
+       if (code == ContactPointSystem.NULL)
+           return null;
+       if (code == ContactPointSystem.PHONE)
       return "phone";
     if (code == ContactPointSystem.FAX)
       return "fax";
@@ -63,7 +65,7 @@ public String toCode(ContactPointSystem code) {
     if (code == ContactPointSystem.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(ContactPointSystem code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointUseEnumFactory.java
index d16f151371..afe09ccb22 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactPointUseEnumFactory.java
@@ -52,7 +52,9 @@ public ContactPointUse fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ContactPointUse code) {
-    if (code == ContactPointUse.HOME)
+       if (code == ContactPointUse.NULL)
+           return null;
+       if (code == ContactPointUse.HOME)
       return "home";
     if (code == ContactPointUse.WORK)
       return "work";
@@ -63,7 +65,7 @@ public String toCode(ContactPointUse code) {
     if (code == ContactPointUse.MOBILE)
       return "mobile";
     return "?";
-  }
+   }
 
   public String toSystem(ContactPointUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactentityTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactentityTypeEnumFactory.java
index 7876d955fa..638a4eac5a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactentityTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContactentityTypeEnumFactory.java
@@ -54,7 +54,9 @@ public ContactentityType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(ContactentityType code) {
-    if (code == ContactentityType.BILL)
+       if (code == ContactentityType.NULL)
+           return null;
+       if (code == ContactentityType.BILL)
       return "BILL";
     if (code == ContactentityType.ADMIN)
       return "ADMIN";
@@ -67,7 +69,7 @@ public String toCode(ContactentityType code) {
     if (code == ContactentityType.PRESS)
       return "PRESS";
     return "?";
-  }
+   }
 
   public String toSystem(ContactentityType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContentTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContentTypeEnumFactory.java
index 6cc31f0a79..d69bcb82bd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContentTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContentTypeEnumFactory.java
@@ -46,12 +46,14 @@ public ContentType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ContentType code) {
-    if (code == ContentType.XML)
+       if (code == ContentType.NULL)
+           return null;
+       if (code == ContentType.XML)
       return "xml";
     if (code == ContentType.JSON)
       return "json";
     return "?";
-  }
+   }
 
   public String toSystem(ContentType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActionEnumFactory.java
index fee0c29ae9..14cfd06138 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActionEnumFactory.java
@@ -46,12 +46,14 @@ public ContractAction fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ContractAction code) {
-    if (code == ContractAction.ACTIONA)
+       if (code == ContractAction.NULL)
+           return null;
+       if (code == ContractAction.ACTIONA)
       return "action-a";
     if (code == ContractAction.ACTIONB)
       return "action-b";
     return "?";
-  }
+   }
 
   public String toSystem(ContractAction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActorroleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActorroleEnumFactory.java
index 55b3ffb440..5652ed8439 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActorroleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractActorroleEnumFactory.java
@@ -46,12 +46,14 @@ public ContractActorrole fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(ContractActorrole code) {
-    if (code == ContractActorrole.PRACTITIONER)
+       if (code == ContractActorrole.NULL)
+           return null;
+       if (code == ContractActorrole.PRACTITIONER)
       return "practitioner";
     if (code == ContractActorrole.PATIENT)
       return "patient";
     return "?";
-  }
+   }
 
   public String toSystem(ContractActorrole code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSignerTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSignerTypeEnumFactory.java
index 39af9de13c..1aa23ab1a3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSignerTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSignerTypeEnumFactory.java
@@ -138,7 +138,9 @@ public ContractSignerType fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ContractSignerType code) {
-    if (code == ContractSignerType.AMENDER)
+       if (code == ContractSignerType.NULL)
+           return null;
+       if (code == ContractSignerType.AMENDER)
       return "AMENDER";
     if (code == ContractSignerType.AUTHN)
       return "AUTHN";
@@ -235,7 +237,7 @@ public String toCode(ContractSignerType code) {
     if (code == ContractSignerType.WIT)
       return "WIT";
     return "?";
-  }
+   }
 
   public String toSystem(ContractSignerType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSubtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSubtypeEnumFactory.java
index b71377c0c1..a3be72a90d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSubtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractSubtypeEnumFactory.java
@@ -46,12 +46,14 @@ public ContractSubtype fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ContractSubtype code) {
-    if (code == ContractSubtype.DISCLOSURECA)
+       if (code == ContractSubtype.NULL)
+           return null;
+       if (code == ContractSubtype.DISCLOSURECA)
       return "disclosure-CA";
     if (code == ContractSubtype.DISCLOSUREUS)
       return "disclosure-US";
     return "?";
-  }
+   }
 
   public String toSystem(ContractSubtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermSubtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermSubtypeEnumFactory.java
index 4f71566b47..4eac72fc82 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermSubtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermSubtypeEnumFactory.java
@@ -48,14 +48,16 @@ public ContractTermSubtype fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(ContractTermSubtype code) {
-    if (code == ContractTermSubtype.ORALHEALTHBASIC)
+       if (code == ContractTermSubtype.NULL)
+           return null;
+       if (code == ContractTermSubtype.ORALHEALTHBASIC)
       return "OralHealth-Basic";
     if (code == ContractTermSubtype.ORALHEALTHMAJOR)
       return "OralHealth-Major";
     if (code == ContractTermSubtype.ORALHEALTHORTHODONTIC)
       return "OralHealth-Orthodontic";
     return "?";
-  }
+   }
 
   public String toSystem(ContractTermSubtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermTypeEnumFactory.java
index 39929deb4f..bb227129fa 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTermTypeEnumFactory.java
@@ -46,12 +46,14 @@ public ContractTermType fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(ContractTermType code) {
-    if (code == ContractTermType.ORALHEALTH)
+       if (code == ContractTermType.NULL)
+           return null;
+       if (code == ContractTermType.ORALHEALTH)
       return "OralHealth";
     if (code == ContractTermType.VISION)
       return "Vision";
     return "?";
-  }
+   }
 
   public String toSystem(ContractTermType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTypeEnumFactory.java
index cc99f85eb8..3228df0ccd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ContractTypeEnumFactory.java
@@ -46,12 +46,14 @@ public ContractType fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ContractType code) {
-    if (code == ContractType.PRIVACY)
+       if (code == ContractType.NULL)
+           return null;
+       if (code == ContractType.PRIVACY)
       return "privacy";
     if (code == ContractType.DISCLOSURE)
       return "disclosure";
     return "?";
-  }
+   }
 
   public String toSystem(ContractType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CopyNumberEventEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CopyNumberEventEnumFactory.java
index 0483984000..532ee3924f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CopyNumberEventEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CopyNumberEventEnumFactory.java
@@ -48,14 +48,16 @@ public CopyNumberEvent fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(CopyNumberEvent code) {
-    if (code == CopyNumberEvent.AMP)
+       if (code == CopyNumberEvent.NULL)
+           return null;
+       if (code == CopyNumberEvent.AMP)
       return "amp";
     if (code == CopyNumberEvent.DEL)
       return "del";
     if (code == CopyNumberEvent.LOF)
       return "lof";
     return "?";
-  }
+   }
 
   public String toSystem(CopyNumberEvent code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CoverageExceptionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CoverageExceptionEnumFactory.java
index 04de406da1..21d849840a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CoverageExceptionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CoverageExceptionEnumFactory.java
@@ -46,12 +46,14 @@ public CoverageException fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(CoverageException code) {
-    if (code == CoverageException.STUDENT)
+       if (code == CoverageException.NULL)
+           return null;
+       if (code == CoverageException.STUDENT)
       return "student";
     if (code == CoverageException.DISABLED)
       return "disabled";
     return "?";
-  }
+   }
 
   public String toSystem(CoverageException code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CqifCqifTriggerTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CqifCqifTriggerTypeEnumFactory.java
index 37349261f1..ab3202537b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CqifCqifTriggerTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/CqifCqifTriggerTypeEnumFactory.java
@@ -56,7 +56,9 @@ public CqifCqifTriggerType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(CqifCqifTriggerType code) {
-    if (code == CqifCqifTriggerType.NAMEDEVENT)
+       if (code == CqifCqifTriggerType.NULL)
+           return null;
+       if (code == CqifCqifTriggerType.NAMEDEVENT)
       return "named-event";
     if (code == CqifCqifTriggerType.PERIODIC)
       return "periodic";
@@ -71,7 +73,7 @@ public String toCode(CqifCqifTriggerType code) {
     if (code == CqifCqifTriggerType.DATAACCESSENDED)
       return "data-access-ended";
     return "?";
-  }
+   }
 
   public String toSystem(CqifCqifTriggerType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DWebTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DWebTypeEnumFactory.java
index ee7ce1c5d8..cf387c7210 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DWebTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DWebTypeEnumFactory.java
@@ -50,7 +50,9 @@ public DWebType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(DWebType code) {
-    if (code == DWebType.WADORS)
+       if (code == DWebType.NULL)
+           return null;
+       if (code == DWebType.WADORS)
       return "WADO-RS";
     if (code == DWebType.WADOURI)
       return "WADO-URI";
@@ -59,7 +61,7 @@ public String toCode(DWebType code) {
     if (code == DWebType.WADOWS)
       return "WADO-WS";
     return "?";
-  }
+   }
 
   public String toSystem(DWebType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataAbsentReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataAbsentReasonEnumFactory.java
index 8f0fe10fa0..2c72974ea0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataAbsentReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataAbsentReasonEnumFactory.java
@@ -60,7 +60,9 @@ public DataAbsentReason fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(DataAbsentReason code) {
-    if (code == DataAbsentReason.UNKNOWN)
+       if (code == DataAbsentReason.NULL)
+           return null;
+       if (code == DataAbsentReason.UNKNOWN)
       return "unknown";
     if (code == DataAbsentReason.ASKED)
       return "asked";
@@ -79,7 +81,7 @@ public String toCode(DataAbsentReason code) {
     if (code == DataAbsentReason.NAN)
       return "NaN";
     return "?";
-  }
+   }
 
   public String toSystem(DataAbsentReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataTypesEnumFactory.java
index ff06d9917e..58e159cd24 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataTypesEnumFactory.java
@@ -144,7 +144,9 @@ public DataTypes fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(DataTypes code) {
-    if (code == DataTypes.ACTIONDEFINITION)
+       if (code == DataTypes.NULL)
+           return null;
+       if (code == DataTypes.ACTIONDEFINITION)
       return "ActionDefinition";
     if (code == DataTypes.ADDRESS)
       return "Address";
@@ -247,7 +249,7 @@ public String toCode(DataTypes code) {
     if (code == DataTypes.XHTML)
       return "xhtml";
     return "?";
-  }
+   }
 
   public String toSystem(DataTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataelementStringencyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataelementStringencyEnumFactory.java
index 621cea19e7..9a561a6ecb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataelementStringencyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DataelementStringencyEnumFactory.java
@@ -54,7 +54,9 @@ public DataelementStringency fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(DataelementStringency code) {
-    if (code == DataelementStringency.COMPARABLE)
+       if (code == DataelementStringency.NULL)
+           return null;
+       if (code == DataelementStringency.COMPARABLE)
       return "comparable";
     if (code == DataelementStringency.FULLYSPECIFIED)
       return "fully-specified";
@@ -67,7 +69,7 @@ public String toCode(DataelementStringency code) {
     if (code == DataelementStringency.FLEXIBLE)
       return "flexible";
     return "?";
-  }
+   }
 
   public String toSystem(DataelementStringency code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DaysOfWeekEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DaysOfWeekEnumFactory.java
index 4b464d1072..723ad54b30 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DaysOfWeekEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DaysOfWeekEnumFactory.java
@@ -56,7 +56,9 @@ public DaysOfWeek fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(DaysOfWeek code) {
-    if (code == DaysOfWeek.MON)
+       if (code == DaysOfWeek.NULL)
+           return null;
+       if (code == DaysOfWeek.MON)
       return "mon";
     if (code == DaysOfWeek.TUE)
       return "tue";
@@ -71,7 +73,7 @@ public String toCode(DaysOfWeek code) {
     if (code == DaysOfWeek.SUN)
       return "sun";
     return "?";
-  }
+   }
 
   public String toSystem(DaysOfWeek code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DetectedissueSeverityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DetectedissueSeverityEnumFactory.java
index 0040a3b47c..63881b3ce5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DetectedissueSeverityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DetectedissueSeverityEnumFactory.java
@@ -48,14 +48,16 @@ public DetectedissueSeverity fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(DetectedissueSeverity code) {
-    if (code == DetectedissueSeverity.HIGH)
+       if (code == DetectedissueSeverity.NULL)
+           return null;
+       if (code == DetectedissueSeverity.HIGH)
       return "high";
     if (code == DetectedissueSeverity.MODERATE)
       return "moderate";
     if (code == DetectedissueSeverity.LOW)
       return "low";
     return "?";
-  }
+   }
 
   public String toSystem(DetectedissueSeverity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceActionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceActionEnumFactory.java
index 222f43f437..2629c2fbe6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceActionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceActionEnumFactory.java
@@ -48,14 +48,16 @@ public DeviceAction fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(DeviceAction code) {
-    if (code == DeviceAction.IMPLANTED)
+       if (code == DeviceAction.NULL)
+           return null;
+       if (code == DeviceAction.IMPLANTED)
       return "implanted";
     if (code == DeviceAction.EXPLANTED)
       return "explanted";
     if (code == DeviceAction.MANIPULATED)
       return "manipulated";
     return "?";
-  }
+   }
 
   public String toSystem(DeviceAction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestPriorityEnumFactory.java
index f818949c68..b2a6a44ab4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestPriorityEnumFactory.java
@@ -50,7 +50,9 @@ public DeviceUseRequestPriority fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(DeviceUseRequestPriority code) {
-    if (code == DeviceUseRequestPriority.ROUTINE)
+       if (code == DeviceUseRequestPriority.NULL)
+           return null;
+       if (code == DeviceUseRequestPriority.ROUTINE)
       return "routine";
     if (code == DeviceUseRequestPriority.URGENT)
       return "urgent";
@@ -59,7 +61,7 @@ public String toCode(DeviceUseRequestPriority code) {
     if (code == DeviceUseRequestPriority.ASAP)
       return "asap";
     return "?";
-  }
+   }
 
   public String toSystem(DeviceUseRequestPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestStatusEnumFactory.java
index f6266e7a4e..43bae00ea1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DeviceUseRequestStatusEnumFactory.java
@@ -62,7 +62,9 @@ public DeviceUseRequestStatus fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(DeviceUseRequestStatus code) {
-    if (code == DeviceUseRequestStatus.PROPOSED)
+       if (code == DeviceUseRequestStatus.NULL)
+           return null;
+       if (code == DeviceUseRequestStatus.PROPOSED)
       return "proposed";
     if (code == DeviceUseRequestStatus.PLANNED)
       return "planned";
@@ -83,7 +85,7 @@ public String toCode(DeviceUseRequestStatus code) {
     if (code == DeviceUseRequestStatus.ABORTED)
       return "aborted";
     return "?";
-  }
+   }
 
   public String toSystem(DeviceUseRequestStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DevicestatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DevicestatusEnumFactory.java
index 563f64198e..22429e589c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DevicestatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DevicestatusEnumFactory.java
@@ -48,14 +48,16 @@ public Devicestatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(Devicestatus code) {
-    if (code == Devicestatus.AVAILABLE)
+       if (code == Devicestatus.NULL)
+           return null;
+       if (code == Devicestatus.AVAILABLE)
       return "available";
     if (code == Devicestatus.NOTAVAILABLE)
       return "not-available";
     if (code == Devicestatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(Devicestatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderPriorityEnumFactory.java
index 243a821d5a..c25b94c8ab 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderPriorityEnumFactory.java
@@ -50,7 +50,9 @@ public DiagnosticOrderPriority fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(DiagnosticOrderPriority code) {
-    if (code == DiagnosticOrderPriority.ROUTINE)
+       if (code == DiagnosticOrderPriority.NULL)
+           return null;
+       if (code == DiagnosticOrderPriority.ROUTINE)
       return "routine";
     if (code == DiagnosticOrderPriority.URGENT)
       return "urgent";
@@ -59,7 +61,7 @@ public String toCode(DiagnosticOrderPriority code) {
     if (code == DiagnosticOrderPriority.ASAP)
       return "asap";
     return "?";
-  }
+   }
 
   public String toSystem(DiagnosticOrderPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderStatusEnumFactory.java
index e3069c81bc..70d3ef8565 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticOrderStatusEnumFactory.java
@@ -70,7 +70,9 @@ public DiagnosticOrderStatus fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(DiagnosticOrderStatus code) {
-    if (code == DiagnosticOrderStatus.PROPOSED)
+       if (code == DiagnosticOrderStatus.NULL)
+           return null;
+       if (code == DiagnosticOrderStatus.PROPOSED)
       return "proposed";
     if (code == DiagnosticOrderStatus.DRAFT)
       return "draft";
@@ -99,7 +101,7 @@ public String toCode(DiagnosticOrderStatus code) {
     if (code == DiagnosticOrderStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(DiagnosticOrderStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticReportStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticReportStatusEnumFactory.java
index 966ef0d9b5..cd505884dc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticReportStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DiagnosticReportStatusEnumFactory.java
@@ -56,7 +56,9 @@ public DiagnosticReportStatus fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(DiagnosticReportStatus code) {
-    if (code == DiagnosticReportStatus.REGISTERED)
+       if (code == DiagnosticReportStatus.NULL)
+           return null;
+       if (code == DiagnosticReportStatus.REGISTERED)
       return "registered";
     if (code == DiagnosticReportStatus.PARTIAL)
       return "partial";
@@ -71,7 +73,7 @@ public String toCode(DiagnosticReportStatus code) {
     if (code == DiagnosticReportStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(DiagnosticReportStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaSubtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaSubtypeEnumFactory.java
index 10d06cf303..0b5e86168b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaSubtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaSubtypeEnumFactory.java
@@ -58,7 +58,9 @@ public DigitalMediaSubtype fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(DigitalMediaSubtype code) {
-    if (code == DigitalMediaSubtype.DIAGRAM)
+       if (code == DigitalMediaSubtype.NULL)
+           return null;
+       if (code == DigitalMediaSubtype.DIAGRAM)
       return "diagram";
     if (code == DigitalMediaSubtype.FAX)
       return "fax";
@@ -75,7 +77,7 @@ public String toCode(DigitalMediaSubtype code) {
     if (code == DigitalMediaSubtype.FACE)
       return "face";
     return "?";
-  }
+   }
 
   public String toSystem(DigitalMediaSubtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaTypeEnumFactory.java
index 760e046146..b19dbf8273 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DigitalMediaTypeEnumFactory.java
@@ -48,14 +48,16 @@ public DigitalMediaType fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(DigitalMediaType code) {
-    if (code == DigitalMediaType.PHOTO)
+       if (code == DigitalMediaType.NULL)
+           return null;
+       if (code == DigitalMediaType.PHOTO)
       return "photo";
     if (code == DigitalMediaType.VIDEO)
       return "video";
     if (code == DigitalMediaType.AUDIO)
       return "audio";
     return "?";
-  }
+   }
 
   public String toSystem(DigitalMediaType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentModeEnumFactory.java
index f8d260bab4..1e5a2edbc7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentModeEnumFactory.java
@@ -46,12 +46,14 @@ public DocumentMode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(DocumentMode code) {
-    if (code == DocumentMode.PRODUCER)
+       if (code == DocumentMode.NULL)
+           return null;
+       if (code == DocumentMode.PRODUCER)
       return "producer";
     if (code == DocumentMode.CONSUMER)
       return "consumer";
     return "?";
-  }
+   }
 
   public String toSystem(DocumentMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentReferenceStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentReferenceStatusEnumFactory.java
index d344c759cf..5bd5ffa1c2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentReferenceStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentReferenceStatusEnumFactory.java
@@ -48,14 +48,16 @@ public DocumentReferenceStatus fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(DocumentReferenceStatus code) {
-    if (code == DocumentReferenceStatus.CURRENT)
+       if (code == DocumentReferenceStatus.NULL)
+           return null;
+       if (code == DocumentReferenceStatus.CURRENT)
       return "current";
     if (code == DocumentReferenceStatus.SUPERSEDED)
       return "superseded";
     if (code == DocumentReferenceStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(DocumentReferenceStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentRelationshipTypeEnumFactory.java
index a98f96adde..6bcd58a118 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/DocumentRelationshipTypeEnumFactory.java
@@ -50,7 +50,9 @@ public DocumentRelationshipType fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(DocumentRelationshipType code) {
-    if (code == DocumentRelationshipType.REPLACES)
+       if (code == DocumentRelationshipType.NULL)
+           return null;
+       if (code == DocumentRelationshipType.REPLACES)
       return "replaces";
     if (code == DocumentRelationshipType.TRANSFORMS)
       return "transforms";
@@ -59,7 +61,7 @@ public String toCode(DocumentRelationshipType code) {
     if (code == DocumentRelationshipType.APPENDS)
       return "appends";
     return "?";
-  }
+   }
 
   public String toSystem(DocumentRelationshipType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterAdmitSourceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterAdmitSourceEnumFactory.java
index ba20bdef82..e260a022ec 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterAdmitSourceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterAdmitSourceEnumFactory.java
@@ -62,7 +62,9 @@ public EncounterAdmitSource fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(EncounterAdmitSource code) {
-    if (code == EncounterAdmitSource.HOSPTRANS)
+       if (code == EncounterAdmitSource.NULL)
+           return null;
+       if (code == EncounterAdmitSource.HOSPTRANS)
       return "hosp-trans";
     if (code == EncounterAdmitSource.EMD)
       return "emd";
@@ -83,7 +85,7 @@ public String toCode(EncounterAdmitSource code) {
     if (code == EncounterAdmitSource.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterAdmitSource code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterClassEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterClassEnumFactory.java
index 813a42def5..c897f7178d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterClassEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterClassEnumFactory.java
@@ -60,7 +60,9 @@ public EncounterClass fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(EncounterClass code) {
-    if (code == EncounterClass.INPATIENT)
+       if (code == EncounterClass.NULL)
+           return null;
+       if (code == EncounterClass.INPATIENT)
       return "inpatient";
     if (code == EncounterClass.OUTPATIENT)
       return "outpatient";
@@ -79,7 +81,7 @@ public String toCode(EncounterClass code) {
     if (code == EncounterClass.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterClass code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDietEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDietEnumFactory.java
index d44553a4bf..9ce1fedee7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDietEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDietEnumFactory.java
@@ -56,7 +56,9 @@ public EncounterDiet fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(EncounterDiet code) {
-    if (code == EncounterDiet.VEGETARIAN)
+       if (code == EncounterDiet.NULL)
+           return null;
+       if (code == EncounterDiet.VEGETARIAN)
       return "vegetarian";
     if (code == EncounterDiet.DAIRYFREE)
       return "dairy-free";
@@ -71,7 +73,7 @@ public String toCode(EncounterDiet code) {
     if (code == EncounterDiet.KOSHER)
       return "kosher";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterDiet code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDischargeDispositionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDischargeDispositionEnumFactory.java
index 80208ffb26..235105f3a7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDischargeDispositionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterDischargeDispositionEnumFactory.java
@@ -60,7 +60,9 @@ public EncounterDischargeDisposition fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(EncounterDischargeDisposition code) {
-    if (code == EncounterDischargeDisposition.HOME)
+       if (code == EncounterDischargeDisposition.NULL)
+           return null;
+       if (code == EncounterDischargeDisposition.HOME)
       return "home";
     if (code == EncounterDischargeDisposition.OTHERHCF)
       return "other-hcf";
@@ -79,7 +81,7 @@ public String toCode(EncounterDischargeDisposition code) {
     if (code == EncounterDischargeDisposition.OTH)
       return "oth";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterDischargeDisposition code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterLocationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterLocationStatusEnumFactory.java
index 9025220668..e5a771601c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterLocationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterLocationStatusEnumFactory.java
@@ -50,7 +50,9 @@ public EncounterLocationStatus fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(EncounterLocationStatus code) {
-    if (code == EncounterLocationStatus.PLANNED)
+       if (code == EncounterLocationStatus.NULL)
+           return null;
+       if (code == EncounterLocationStatus.PLANNED)
       return "planned";
     if (code == EncounterLocationStatus.ACTIVE)
       return "active";
@@ -59,7 +61,7 @@ public String toCode(EncounterLocationStatus code) {
     if (code == EncounterLocationStatus.COMPLETED)
       return "completed";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterLocationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterParticipantTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterParticipantTypeEnumFactory.java
index e42884f1f3..e6b987dba3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterParticipantTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterParticipantTypeEnumFactory.java
@@ -46,12 +46,14 @@ public EncounterParticipantType fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(EncounterParticipantType code) {
-    if (code == EncounterParticipantType.TRANSLATOR)
+       if (code == EncounterParticipantType.NULL)
+           return null;
+       if (code == EncounterParticipantType.TRANSLATOR)
       return "translator";
     if (code == EncounterParticipantType.EMERGENCY)
       return "emergency";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterParticipantType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterPriorityEnumFactory.java
index bed0358b38..d4a8f29583 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterPriorityEnumFactory.java
@@ -52,7 +52,9 @@ public EncounterPriority fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(EncounterPriority code) {
-    if (code == EncounterPriority.IMM)
+       if (code == EncounterPriority.NULL)
+           return null;
+       if (code == EncounterPriority.IMM)
       return "imm";
     if (code == EncounterPriority.EMG)
       return "emg";
@@ -63,7 +65,7 @@ public String toCode(EncounterPriority code) {
     if (code == EncounterPriority.NOURG)
       return "no-urg";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterSpecialArrangementsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterSpecialArrangementsEnumFactory.java
index 5c30c03121..4861579d84 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterSpecialArrangementsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterSpecialArrangementsEnumFactory.java
@@ -52,7 +52,9 @@ public EncounterSpecialArrangements fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(EncounterSpecialArrangements code) {
-    if (code == EncounterSpecialArrangements.WHEEL)
+       if (code == EncounterSpecialArrangements.NULL)
+           return null;
+       if (code == EncounterSpecialArrangements.WHEEL)
       return "wheel";
     if (code == EncounterSpecialArrangements.STRET)
       return "stret";
@@ -63,7 +65,7 @@ public String toCode(EncounterSpecialArrangements code) {
     if (code == EncounterSpecialArrangements.DOG)
       return "dog";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterSpecialArrangements code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterStateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterStateEnumFactory.java
index b20af26cf3..2212902a1c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterStateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterStateEnumFactory.java
@@ -54,7 +54,9 @@ public EncounterState fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(EncounterState code) {
-    if (code == EncounterState.PLANNED)
+       if (code == EncounterState.NULL)
+           return null;
+       if (code == EncounterState.PLANNED)
       return "planned";
     if (code == EncounterState.ARRIVED)
       return "arrived";
@@ -67,7 +69,7 @@ public String toCode(EncounterState code) {
     if (code == EncounterState.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterState code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterTypeEnumFactory.java
index d7750ca3f3..16c20ef69a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EncounterTypeEnumFactory.java
@@ -50,7 +50,9 @@ public EncounterType fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(EncounterType code) {
-    if (code == EncounterType.ADMS)
+       if (code == EncounterType.NULL)
+           return null;
+       if (code == EncounterType.ADMS)
       return "ADMS";
     if (code == EncounterType.BD_BMCLIN)
       return "BD/BM-clin";
@@ -59,7 +61,7 @@ public String toCode(EncounterType code) {
     if (code == EncounterType.OKI)
       return "OKI";
     return "?";
-  }
+   }
 
   public String toSystem(EncounterType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EndpointStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EndpointStatusEnumFactory.java
index 71599e166b..6da07b7ce7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EndpointStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EndpointStatusEnumFactory.java
@@ -50,7 +50,9 @@ public EndpointStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(EndpointStatus code) {
-    if (code == EndpointStatus.ACTIVE)
+       if (code == EndpointStatus.NULL)
+           return null;
+       if (code == EndpointStatus.ACTIVE)
       return "active";
     if (code == EndpointStatus.SUSPENDED)
       return "suspended";
@@ -59,7 +61,7 @@ public String toCode(EndpointStatus code) {
     if (code == EndpointStatus.OFF)
       return "off";
     return "?";
-  }
+   }
 
   public String toSystem(EndpointStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EntformulaAdditiveEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EntformulaAdditiveEnumFactory.java
index ceafd7b0cd..2700e5ec53 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EntformulaAdditiveEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EntformulaAdditiveEnumFactory.java
@@ -52,7 +52,9 @@ public EntformulaAdditive fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(EntformulaAdditive code) {
-    if (code == EntformulaAdditive.LIPID)
+       if (code == EntformulaAdditive.NULL)
+           return null;
+       if (code == EntformulaAdditive.LIPID)
       return "lipid";
     if (code == EntformulaAdditive.PROTEIN)
       return "protein";
@@ -63,7 +65,7 @@ public String toCode(EntformulaAdditive code) {
     if (code == EntformulaAdditive.WATER)
       return "water";
     return "?";
-  }
+   }
 
   public String toSystem(EntformulaAdditive code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EpisodeOfCareStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EpisodeOfCareStatusEnumFactory.java
index 3d21354535..974a615d93 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EpisodeOfCareStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/EpisodeOfCareStatusEnumFactory.java
@@ -54,7 +54,9 @@ public EpisodeOfCareStatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(EpisodeOfCareStatus code) {
-    if (code == EpisodeOfCareStatus.PLANNED)
+       if (code == EpisodeOfCareStatus.NULL)
+           return null;
+       if (code == EpisodeOfCareStatus.PLANNED)
       return "planned";
     if (code == EpisodeOfCareStatus.WAITLIST)
       return "waitlist";
@@ -67,7 +69,7 @@ public String toCode(EpisodeOfCareStatus code) {
     if (code == EpisodeOfCareStatus.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(EpisodeOfCareStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExOnsettypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExOnsettypeEnumFactory.java
index 37062c50dd..2e6ae97ccc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExOnsettypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExOnsettypeEnumFactory.java
@@ -48,14 +48,16 @@ public ExOnsettype fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ExOnsettype code) {
-    if (code == ExOnsettype.LXM)
+       if (code == ExOnsettype.NULL)
+           return null;
+       if (code == ExOnsettype.LXM)
       return "LXM";
     if (code == ExOnsettype.SYM)
       return "SYM";
     if (code == ExOnsettype.LMN)
       return "LMN";
     return "?";
-  }
+   }
 
   public String toSystem(ExOnsettype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExProgramCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExProgramCodeEnumFactory.java
index bacae46595..a94b7f819a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExProgramCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExProgramCodeEnumFactory.java
@@ -48,14 +48,16 @@ public ExProgramCode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ExProgramCode code) {
-    if (code == ExProgramCode.AS)
+       if (code == ExProgramCode.NULL)
+           return null;
+       if (code == ExProgramCode.AS)
       return "AS";
     if (code == ExProgramCode.HD)
       return "HD";
     if (code == ExProgramCode.AUSCR)
       return "AUSCR";
     return "?";
-  }
+   }
 
   public String toSystem(ExProgramCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExtensionContextEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExtensionContextEnumFactory.java
index 18264d4c00..8858858ff9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExtensionContextEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ExtensionContextEnumFactory.java
@@ -48,14 +48,16 @@ public ExtensionContext fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(ExtensionContext code) {
-    if (code == ExtensionContext.RESOURCE)
+       if (code == ExtensionContext.NULL)
+           return null;
+       if (code == ExtensionContext.RESOURCE)
       return "resource";
     if (code == ExtensionContext.DATATYPE)
       return "datatype";
     if (code == ExtensionContext.EXTENSION)
       return "extension";
     return "?";
-  }
+   }
 
   public String toSystem(ExtensionContext code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FilterOperatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FilterOperatorEnumFactory.java
index fee1f76ed2..c73916123c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FilterOperatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FilterOperatorEnumFactory.java
@@ -54,7 +54,9 @@ public FilterOperator fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(FilterOperator code) {
-    if (code == FilterOperator.EQUAL)
+       if (code == FilterOperator.NULL)
+           return null;
+       if (code == FilterOperator.EQUAL)
       return "=";
     if (code == FilterOperator.ISA)
       return "is-a";
@@ -67,7 +69,7 @@ public String toCode(FilterOperator code) {
     if (code == FilterOperator.NOTIN)
       return "not-in";
     return "?";
-  }
+   }
 
   public String toSystem(FilterOperator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagCategoryEnumFactory.java
index db20e16b9e..dc9083e35d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagCategoryEnumFactory.java
@@ -52,7 +52,9 @@ public FlagCategory fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(FlagCategory code) {
-    if (code == FlagCategory.DIET)
+       if (code == FlagCategory.NULL)
+           return null;
+       if (code == FlagCategory.DIET)
       return "diet";
     if (code == FlagCategory.DRUG)
       return "drug";
@@ -63,7 +65,7 @@ public String toCode(FlagCategory code) {
     if (code == FlagCategory.CONTACT)
       return "contact";
     return "?";
-  }
+   }
 
   public String toSystem(FlagCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagPriorityEnumFactory.java
index f4c1f64a7d..36c33bafcd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagPriorityEnumFactory.java
@@ -50,7 +50,9 @@ public FlagPriority fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(FlagPriority code) {
-    if (code == FlagPriority.PN)
+       if (code == FlagPriority.NULL)
+           return null;
+       if (code == FlagPriority.PN)
       return "PN";
     if (code == FlagPriority.PL)
       return "PL";
@@ -59,7 +61,7 @@ public String toCode(FlagPriority code) {
     if (code == FlagPriority.PH)
       return "PH";
     return "?";
-  }
+   }
 
   public String toSystem(FlagPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagStatusEnumFactory.java
index a426de344a..126ca610a8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FlagStatusEnumFactory.java
@@ -48,14 +48,16 @@ public FlagStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(FlagStatus code) {
-    if (code == FlagStatus.ACTIVE)
+       if (code == FlagStatus.NULL)
+           return null;
+       if (code == FlagStatus.ACTIVE)
       return "active";
     if (code == FlagStatus.INACTIVE)
       return "inactive";
     if (code == FlagStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(FlagStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FmConditionsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FmConditionsEnumFactory.java
index bff7ecb36c..2d8337ca35 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FmConditionsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FmConditionsEnumFactory.java
@@ -44,10 +44,12 @@ public FmConditions fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(FmConditions code) {
-    if (code == FmConditions._123987)
+       if (code == FmConditions.NULL)
+           return null;
+       if (code == FmConditions._123987)
       return "123987";
     return "?";
-  }
+   }
 
   public String toSystem(FmConditions code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FormsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FormsEnumFactory.java
index dc447a98d6..b63c1758c5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FormsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FormsEnumFactory.java
@@ -46,12 +46,14 @@ public Forms fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Forms code) {
-    if (code == Forms._1)
+       if (code == Forms.NULL)
+           return null;
+       if (code == Forms._1)
       return "1";
     if (code == Forms._2)
       return "2";
     return "?";
-  }
+   }
 
   public String toSystem(Forms code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FundsreserveEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FundsreserveEnumFactory.java
index ed744b76c8..e6021aac4c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FundsreserveEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/FundsreserveEnumFactory.java
@@ -48,14 +48,16 @@ public Fundsreserve fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(Fundsreserve code) {
-    if (code == Fundsreserve.PATIENT)
+       if (code == Fundsreserve.NULL)
+           return null;
+       if (code == Fundsreserve.PATIENT)
       return "patient";
     if (code == Fundsreserve.PROVIDER)
       return "provider";
     if (code == Fundsreserve.NONE)
       return "none";
     return "?";
-  }
+   }
 
   public String toSystem(Fundsreserve code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GaoEvaluationResultCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GaoEvaluationResultCodeEnumFactory.java
index dd8f606625..8d096e819b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GaoEvaluationResultCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GaoEvaluationResultCodeEnumFactory.java
@@ -54,7 +54,9 @@ public GaoEvaluationResultCode fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(GaoEvaluationResultCode code) {
-    if (code == GaoEvaluationResultCode.WITHIN)
+       if (code == GaoEvaluationResultCode.NULL)
+           return null;
+       if (code == GaoEvaluationResultCode.WITHIN)
       return "within";
     if (code == GaoEvaluationResultCode.OUTSIDE)
       return "outside";
@@ -67,7 +69,7 @@ public String toCode(GaoEvaluationResultCode code) {
     if (code == GaoEvaluationResultCode.NOTCOVERED)
       return "notcovered";
     return "?";
-  }
+   }
 
   public String toSystem(GaoEvaluationResultCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalAcceptanceStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalAcceptanceStatusEnumFactory.java
index 68af07044c..5519596098 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalAcceptanceStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalAcceptanceStatusEnumFactory.java
@@ -48,14 +48,16 @@ public GoalAcceptanceStatus fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(GoalAcceptanceStatus code) {
-    if (code == GoalAcceptanceStatus.AGREE)
+       if (code == GoalAcceptanceStatus.NULL)
+           return null;
+       if (code == GoalAcceptanceStatus.AGREE)
       return "agree";
     if (code == GoalAcceptanceStatus.DISAGREE)
       return "disagree";
     if (code == GoalAcceptanceStatus.PENDING)
       return "pending";
     return "?";
-  }
+   }
 
   public String toSystem(GoalAcceptanceStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalCategoryEnumFactory.java
index 665eb7b694..4b3819e22d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalCategoryEnumFactory.java
@@ -52,7 +52,9 @@ public GoalCategory fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(GoalCategory code) {
-    if (code == GoalCategory.DIETARY)
+       if (code == GoalCategory.NULL)
+           return null;
+       if (code == GoalCategory.DIETARY)
       return "dietary";
     if (code == GoalCategory.SAFETY)
       return "safety";
@@ -63,7 +65,7 @@ public String toCode(GoalCategory code) {
     if (code == GoalCategory.PHYSIOTHERAPY)
       return "physiotherapy";
     return "?";
-  }
+   }
 
   public String toSystem(GoalCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalPriorityEnumFactory.java
index 867f98d378..9c7ff404fe 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalPriorityEnumFactory.java
@@ -48,14 +48,16 @@ public GoalPriority fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(GoalPriority code) {
-    if (code == GoalPriority.HIGH)
+       if (code == GoalPriority.NULL)
+           return null;
+       if (code == GoalPriority.HIGH)
       return "high";
     if (code == GoalPriority.MEDIUM)
       return "medium";
     if (code == GoalPriority.LOW)
       return "low";
     return "?";
-  }
+   }
 
   public String toSystem(GoalPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalRelationshipTypeEnumFactory.java
index ca21f3bf12..efc6413bd1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalRelationshipTypeEnumFactory.java
@@ -52,7 +52,9 @@ public GoalRelationshipType fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(GoalRelationshipType code) {
-    if (code == GoalRelationshipType.PREDECESSOR)
+       if (code == GoalRelationshipType.NULL)
+           return null;
+       if (code == GoalRelationshipType.PREDECESSOR)
       return "predecessor";
     if (code == GoalRelationshipType.SUCCESSOR)
       return "successor";
@@ -63,7 +65,7 @@ public String toCode(GoalRelationshipType code) {
     if (code == GoalRelationshipType.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(GoalRelationshipType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusEnumFactory.java
index 3157ff341f..9cb8af08e9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusEnumFactory.java
@@ -60,7 +60,9 @@ public GoalStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(GoalStatus code) {
-    if (code == GoalStatus.PROPOSED)
+       if (code == GoalStatus.NULL)
+           return null;
+       if (code == GoalStatus.PROPOSED)
       return "proposed";
     if (code == GoalStatus.PLANNED)
       return "planned";
@@ -79,7 +81,7 @@ public String toCode(GoalStatus code) {
     if (code == GoalStatus.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(GoalStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusReasonEnumFactory.java
index 5b0ed33bd2..1b03f4e8ce 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GoalStatusReasonEnumFactory.java
@@ -50,7 +50,9 @@ public GoalStatusReason fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(GoalStatusReason code) {
-    if (code == GoalStatusReason.SURGERY)
+       if (code == GoalStatusReason.NULL)
+           return null;
+       if (code == GoalStatusReason.SURGERY)
       return "surgery";
     if (code == GoalStatusReason.LIFEEVENT)
       return "life-event";
@@ -59,7 +61,7 @@ public String toCode(GoalStatusReason code) {
     if (code == GoalStatusReason.PATIENTREQUEST)
       return "patient-request";
     return "?";
-  }
+   }
 
   public String toSystem(GoalStatusReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupTypeEnumFactory.java
index e83b71fe96..02df39ed73 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupTypeEnumFactory.java
@@ -54,7 +54,9 @@ public GroupType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(GroupType code) {
-    if (code == GroupType.PERSON)
+       if (code == GroupType.NULL)
+           return null;
+       if (code == GroupType.PERSON)
       return "person";
     if (code == GroupType.ANIMAL)
       return "animal";
@@ -67,7 +69,7 @@ public String toCode(GroupType code) {
     if (code == GroupType.SUBSTANCE)
       return "substance";
     return "?";
-  }
+   }
 
   public String toSystem(GroupType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupingBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupingBehaviorEnumFactory.java
index bc8f73b688..ad2c2743dd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupingBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GroupingBehaviorEnumFactory.java
@@ -48,14 +48,16 @@ public GroupingBehavior fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(GroupingBehavior code) {
-    if (code == GroupingBehavior.VISUALGROUP)
+       if (code == GroupingBehavior.NULL)
+           return null;
+       if (code == GroupingBehavior.VISUALGROUP)
       return "visual-group";
     if (code == GroupingBehavior.LOGICALGROUP)
       return "logical-group";
     if (code == GroupingBehavior.SENTENCEGROUP)
       return "sentence-group";
     return "?";
-  }
+   }
 
   public String toSystem(GroupingBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseActionTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseActionTypeEnumFactory.java
index 5aa8d7761f..d5efb0a975 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseActionTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseActionTypeEnumFactory.java
@@ -50,7 +50,9 @@ public GuidanceResponseActionType fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(GuidanceResponseActionType code) {
-    if (code == GuidanceResponseActionType.CREATE)
+       if (code == GuidanceResponseActionType.NULL)
+           return null;
+       if (code == GuidanceResponseActionType.CREATE)
       return "create";
     if (code == GuidanceResponseActionType.UPDATE)
       return "update";
@@ -59,7 +61,7 @@ public String toCode(GuidanceResponseActionType code) {
     if (code == GuidanceResponseActionType.FIREEVENT)
       return "fire-event";
     return "?";
-  }
+   }
 
   public String toSystem(GuidanceResponseActionType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseStatusEnumFactory.java
index 369409a751..51357b08b3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidanceResponseStatusEnumFactory.java
@@ -52,7 +52,9 @@ public GuidanceResponseStatus fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(GuidanceResponseStatus code) {
-    if (code == GuidanceResponseStatus.SUCCESS)
+       if (code == GuidanceResponseStatus.NULL)
+           return null;
+       if (code == GuidanceResponseStatus.SUCCESS)
       return "success";
     if (code == GuidanceResponseStatus.DATAREQUESTED)
       return "data-requested";
@@ -63,7 +65,7 @@ public String toCode(GuidanceResponseStatus code) {
     if (code == GuidanceResponseStatus.FAILURE)
       return "failure";
     return "?";
-  }
+   }
 
   public String toSystem(GuidanceResponseStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideDependencyTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideDependencyTypeEnumFactory.java
index ef5967d43f..5d2fdd5606 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideDependencyTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideDependencyTypeEnumFactory.java
@@ -46,12 +46,14 @@ public GuideDependencyType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(GuideDependencyType code) {
-    if (code == GuideDependencyType.REFERENCE)
+       if (code == GuideDependencyType.NULL)
+           return null;
+       if (code == GuideDependencyType.REFERENCE)
       return "reference";
     if (code == GuideDependencyType.INCLUSION)
       return "inclusion";
     return "?";
-  }
+   }
 
   public String toSystem(GuideDependencyType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidePageKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidePageKindEnumFactory.java
index fde9f10a69..e7e43d5689 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidePageKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuidePageKindEnumFactory.java
@@ -58,7 +58,9 @@ public GuidePageKind fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(GuidePageKind code) {
-    if (code == GuidePageKind.PAGE)
+       if (code == GuidePageKind.NULL)
+           return null;
+       if (code == GuidePageKind.PAGE)
       return "page";
     if (code == GuidePageKind.EXAMPLE)
       return "example";
@@ -75,7 +77,7 @@ public String toCode(GuidePageKind code) {
     if (code == GuidePageKind.RESOURCE)
       return "resource";
     return "?";
-  }
+   }
 
   public String toSystem(GuidePageKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideResourcePurposeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideResourcePurposeEnumFactory.java
index 8f86639420..2545611cc7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideResourcePurposeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/GuideResourcePurposeEnumFactory.java
@@ -54,7 +54,9 @@ public GuideResourcePurpose fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(GuideResourcePurpose code) {
-    if (code == GuideResourcePurpose.EXAMPLE)
+       if (code == GuideResourcePurpose.NULL)
+           return null;
+       if (code == GuideResourcePurpose.EXAMPLE)
       return "example";
     if (code == GuideResourcePurpose.TERMINOLOGY)
       return "terminology";
@@ -67,7 +69,7 @@ public String toCode(GuideResourcePurpose code) {
     if (code == GuideResourcePurpose.LOGICAL)
       return "logical";
     return "?";
-  }
+   }
 
   public String toSystem(GuideResourcePurpose code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HistoryStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HistoryStatusEnumFactory.java
index 69880cde27..e442bbe3db 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HistoryStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HistoryStatusEnumFactory.java
@@ -50,7 +50,9 @@ public HistoryStatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(HistoryStatus code) {
-    if (code == HistoryStatus.PARTIAL)
+       if (code == HistoryStatus.NULL)
+           return null;
+       if (code == HistoryStatus.PARTIAL)
       return "partial";
     if (code == HistoryStatus.COMPLETED)
       return "completed";
@@ -59,7 +61,7 @@ public String toCode(HistoryStatus code) {
     if (code == HistoryStatus.HEALTHUNKNOWN)
       return "health-unknown";
     return "?";
-  }
+   }
 
   public String toSystem(HistoryStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAbnIntNumericNomEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAbnIntNumericNomEnumFactory.java
index 4c198ab46b..8da233c25a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAbnIntNumericNomEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAbnIntNumericNomEnumFactory.java
@@ -46,12 +46,14 @@ public HspcAbnIntNumericNom fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(HspcAbnIntNumericNom code) {
-    if (code == HspcAbnIntNumericNom.HIGHER)
+       if (code == HspcAbnIntNumericNom.NULL)
+           return null;
+       if (code == HspcAbnIntNumericNom.HIGHER)
       return "higher";
     if (code == HspcAbnIntNumericNom.LOWER)
       return "lower";
     return "?";
-  }
+   }
 
   public String toSystem(HspcAbnIntNumericNom code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAddressUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAddressUseEnumFactory.java
index 8cf5fb6a55..cb4d85a470 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAddressUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAddressUseEnumFactory.java
@@ -64,7 +64,9 @@ public HspcAddressUse fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(HspcAddressUse code) {
-    if (code == HspcAddressUse.BAD)
+       if (code == HspcAddressUse.NULL)
+           return null;
+       if (code == HspcAddressUse.BAD)
       return "BAD";
     if (code == HspcAddressUse.PHYS)
       return "PHYS";
@@ -87,7 +89,7 @@ public String toCode(HspcAddressUse code) {
     if (code == HspcAddressUse.CONF)
       return "CONF";
     return "?";
-  }
+   }
 
   public String toSystem(HspcAddressUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAdmissionSourceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAdmissionSourceEnumFactory.java
index 271ce6e342..deef765f47 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAdmissionSourceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAdmissionSourceEnumFactory.java
@@ -84,7 +84,9 @@ public HspcAdmissionSource fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(HspcAdmissionSource code) {
-    if (code == HspcAdmissionSource._102702)
+       if (code == HspcAdmissionSource.NULL)
+           return null;
+       if (code == HspcAdmissionSource._102702)
       return "102702";
     if (code == HspcAdmissionSource._17567)
       return "17567";
@@ -127,7 +129,7 @@ public String toCode(HspcAdmissionSource code) {
     if (code == HspcAdmissionSource._510105654)
       return "510105654";
     return "?";
-  }
+   }
 
   public String toSystem(HspcAdmissionSource code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceStatusEnumFactory.java
index f48d3e92b4..efec54b3e5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceStatusEnumFactory.java
@@ -48,14 +48,16 @@ public HspcAllergyIntoleranceStatus fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(HspcAllergyIntoleranceStatus code) {
-    if (code == HspcAllergyIntoleranceStatus._1797)
+       if (code == HspcAllergyIntoleranceStatus.NULL)
+           return null;
+       if (code == HspcAllergyIntoleranceStatus._1797)
       return "1797";
     if (code == HspcAllergyIntoleranceStatus._69074)
       return "69074";
     if (code == HspcAllergyIntoleranceStatus._31119)
       return "31119";
     return "?";
-  }
+   }
 
   public String toSystem(HspcAllergyIntoleranceStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceTypeEnumFactory.java
index b5e3cc3efc..59439f9373 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcAllergyIntoleranceTypeEnumFactory.java
@@ -44,10 +44,12 @@ public HspcAllergyIntoleranceType fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(HspcAllergyIntoleranceType code) {
-    if (code == HspcAllergyIntoleranceType._521059339)
+       if (code == HspcAllergyIntoleranceType.NULL)
+           return null;
+       if (code == HspcAllergyIntoleranceType._521059339)
       return "521059339";
     return "?";
-  }
+   }
 
   public String toSystem(HspcAllergyIntoleranceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcArrivalStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcArrivalStatusEnumFactory.java
index 91d669ee20..8b56a48595 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcArrivalStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcArrivalStatusEnumFactory.java
@@ -46,12 +46,14 @@ public HspcArrivalStatus fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(HspcArrivalStatus code) {
-    if (code == HspcArrivalStatus._2000000339)
+       if (code == HspcArrivalStatus.NULL)
+           return null;
+       if (code == HspcArrivalStatus._2000000339)
       return "2000000339";
     if (code == HspcArrivalStatus._51084650)
       return "51084650";
     return "?";
-  }
+   }
 
   public String toSystem(HspcArrivalStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBodytempmethoddeviceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBodytempmethoddeviceEnumFactory.java
index 7d581a6591..adba0759b4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBodytempmethoddeviceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBodytempmethoddeviceEnumFactory.java
@@ -50,7 +50,9 @@ public HspcBodytempmethoddevice fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(HspcBodytempmethoddevice code) {
-    if (code == HspcBodytempmethoddevice._30277)
+       if (code == HspcBodytempmethoddevice.NULL)
+           return null;
+       if (code == HspcBodytempmethoddevice._30277)
       return "30277";
     if (code == HspcBodytempmethoddevice._30522)
       return "30522";
@@ -59,7 +61,7 @@ public String toCode(HspcBodytempmethoddevice code) {
     if (code == HspcBodytempmethoddevice._84301)
       return "84301";
     return "?";
-  }
+   }
 
   public String toSystem(HspcBodytempmethoddevice code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBpmeasmethoddeviceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBpmeasmethoddeviceEnumFactory.java
index a26d943d67..9afe7c50d1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBpmeasmethoddeviceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcBpmeasmethoddeviceEnumFactory.java
@@ -50,7 +50,9 @@ public HspcBpmeasmethoddevice fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(HspcBpmeasmethoddevice code) {
-    if (code == HspcBpmeasmethoddevice._2102)
+       if (code == HspcBpmeasmethoddevice.NULL)
+           return null;
+       if (code == HspcBpmeasmethoddevice._2102)
       return "2102";
     if (code == HspcBpmeasmethoddevice._2162)
       return "2162";
@@ -59,7 +61,7 @@ public String toCode(HspcBpmeasmethoddevice code) {
     if (code == HspcBpmeasmethoddevice._50577434)
       return "50577434";
     return "?";
-  }
+   }
 
   public String toSystem(HspcBpmeasmethoddevice code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcClinicalAssertStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcClinicalAssertStatusEnumFactory.java
index f68f5923bb..9e288cbcb9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcClinicalAssertStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcClinicalAssertStatusEnumFactory.java
@@ -46,12 +46,14 @@ public HspcClinicalAssertStatus fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(HspcClinicalAssertStatus code) {
-    if (code == HspcClinicalAssertStatus._1797)
+       if (code == HspcClinicalAssertStatus.NULL)
+           return null;
+       if (code == HspcClinicalAssertStatus._1797)
       return "1797";
     if (code == HspcClinicalAssertStatus._69074)
       return "69074";
     return "?";
-  }
+   }
 
   public String toSystem(HspcClinicalAssertStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDeltaFlagNumericNomEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDeltaFlagNumericNomEnumFactory.java
index d595974fe7..7baebc57c8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDeltaFlagNumericNomEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDeltaFlagNumericNomEnumFactory.java
@@ -44,10 +44,12 @@ public HspcDeltaFlagNumericNom fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(HspcDeltaFlagNumericNom code) {
-    if (code == HspcDeltaFlagNumericNom.UNCHANGED)
+       if (code == HspcDeltaFlagNumericNom.NULL)
+           return null;
+       if (code == HspcDeltaFlagNumericNom.UNCHANGED)
       return "unchanged";
     return "?";
-  }
+   }
 
   public String toSystem(HspcDeltaFlagNumericNom code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDepartureTransportModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDepartureTransportModeEnumFactory.java
index 7fc5d742fe..db8e8d3122 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDepartureTransportModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcDepartureTransportModeEnumFactory.java
@@ -44,10 +44,12 @@ public HspcDepartureTransportMode fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(HspcDepartureTransportMode code) {
-    if (code == HspcDepartureTransportMode._14586425)
+       if (code == HspcDepartureTransportMode.NULL)
+           return null;
+       if (code == HspcDepartureTransportMode._14586425)
       return "14586425";
     return "?";
-  }
+   }
 
   public String toSystem(HspcDepartureTransportMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcFetalestimationmethodEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcFetalestimationmethodEnumFactory.java
index 6882cd4cf2..9d62d5ae3e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcFetalestimationmethodEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcFetalestimationmethodEnumFactory.java
@@ -46,12 +46,14 @@ public HspcFetalestimationmethod fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(HspcFetalestimationmethod code) {
-    if (code == HspcFetalestimationmethod._103241)
+       if (code == HspcFetalestimationmethod.NULL)
+           return null;
+       if (code == HspcFetalestimationmethod._103241)
       return "103241";
     if (code == HspcFetalestimationmethod._205940)
       return "205940";
     return "?";
-  }
+   }
 
   public String toSystem(HspcFetalestimationmethod code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationConditionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationConditionEnumFactory.java
index 191f00f400..821bbc6354 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationConditionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationConditionEnumFactory.java
@@ -48,14 +48,16 @@ public HspcLocationCondition fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(HspcLocationCondition code) {
-    if (code == HspcLocationCondition._182845)
+       if (code == HspcLocationCondition.NULL)
+           return null;
+       if (code == HspcLocationCondition._182845)
       return "182845";
     if (code == HspcLocationCondition._528112801)
       return "528112801";
     if (code == HspcLocationCondition._182843)
       return "182843";
     return "?";
-  }
+   }
 
   public String toSystem(HspcLocationCondition code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationKeyValueSetEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationKeyValueSetEnumFactory.java
index 6380149bd6..84b0e4fe9a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationKeyValueSetEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationKeyValueSetEnumFactory.java
@@ -46,10 +46,12 @@ public HspcLocationServiceDeliveryLocationKeyValueSet fromCode(String codeString
   }
 
   public String toCode(HspcLocationServiceDeliveryLocationKeyValueSet code) {
-    if (code == HspcLocationServiceDeliveryLocationKeyValueSet._119)
+       if (code == HspcLocationServiceDeliveryLocationKeyValueSet.NULL)
+           return null;
+       if (code == HspcLocationServiceDeliveryLocationKeyValueSet._119)
       return "119";
     return "?";
-  }
+   }
 
   public String toSystem(HspcLocationServiceDeliveryLocationKeyValueSet code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationNameUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationNameUseEnumFactory.java
index 444d553e49..670d407ae4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationNameUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcLocationServiceDeliveryLocationNameUseEnumFactory.java
@@ -45,10 +45,12 @@ public HspcLocationServiceDeliveryLocationNameUse fromCode(String codeString) th
   }
 
   public String toCode(HspcLocationServiceDeliveryLocationNameUse code) {
-    if (code == HspcLocationServiceDeliveryLocationNameUse.ABR)
+       if (code == HspcLocationServiceDeliveryLocationNameUse.NULL)
+           return null;
+       if (code == HspcLocationServiceDeliveryLocationNameUse.ABR)
       return "ABR";
     return "?";
-  }
+   }
 
   public String toSystem(HspcLocationServiceDeliveryLocationNameUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationDataOriginationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationDataOriginationModeEnumFactory.java
index 93851039ed..36f8ec4606 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationDataOriginationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationDataOriginationModeEnumFactory.java
@@ -44,10 +44,12 @@ public HspcObservationDataOriginationMode fromCode(String codeString) throws Ill
   }
 
   public String toCode(HspcObservationDataOriginationMode code) {
-    if (code == HspcObservationDataOriginationMode._14610118)
+       if (code == HspcObservationDataOriginationMode.NULL)
+           return null;
+       if (code == HspcObservationDataOriginationMode._14610118)
       return "14610118";
     return "?";
-  }
+   }
 
   public String toSystem(HspcObservationDataOriginationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightMeasMethodDeviceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightMeasMethodDeviceEnumFactory.java
index 7c4e59aa9b..8e60920940 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightMeasMethodDeviceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightMeasMethodDeviceEnumFactory.java
@@ -53,7 +53,9 @@ public HspcObservationHeightMeasMethodDevice fromCode(String codeString) throws
   }
 
   public String toCode(HspcObservationHeightMeasMethodDevice code) {
-    if (code == HspcObservationHeightMeasMethodDevice._2057)
+       if (code == HspcObservationHeightMeasMethodDevice.NULL)
+           return null;
+       if (code == HspcObservationHeightMeasMethodDevice._2057)
       return "2057";
     if (code == HspcObservationHeightMeasMethodDevice._2058)
       return "2058";
@@ -64,7 +66,7 @@ public String toCode(HspcObservationHeightMeasMethodDevice code) {
     if (code == HspcObservationHeightMeasMethodDevice._521363688)
       return "521363688";
     return "?";
-  }
+   }
 
   public String toSystem(HspcObservationHeightMeasMethodDevice code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightPrecondEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightPrecondEnumFactory.java
index 947c3d7e52..e8084a64d0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightPrecondEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationHeightPrecondEnumFactory.java
@@ -50,7 +50,9 @@ public HspcObservationHeightPrecond fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(HspcObservationHeightPrecond code) {
-    if (code == HspcObservationHeightPrecond._84138)
+       if (code == HspcObservationHeightPrecond.NULL)
+           return null;
+       if (code == HspcObservationHeightPrecond._84138)
       return "84138";
     if (code == HspcObservationHeightPrecond._84139)
       return "84139";
@@ -59,7 +61,7 @@ public String toCode(HspcObservationHeightPrecond code) {
     if (code == HspcObservationHeightPrecond._84141)
       return "84141";
     return "?";
-  }
+   }
 
   public String toSystem(HspcObservationHeightPrecond code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightMeasMethodDeviceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightMeasMethodDeviceEnumFactory.java
index c6caec8ae1..2d07f6d050 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightMeasMethodDeviceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightMeasMethodDeviceEnumFactory.java
@@ -61,7 +61,9 @@ public HspcObservationWeightMeasMethodDevice fromCode(String codeString) throws
   }
 
   public String toCode(HspcObservationWeightMeasMethodDevice code) {
-    if (code == HspcObservationWeightMeasMethodDevice._1964)
+       if (code == HspcObservationWeightMeasMethodDevice.NULL)
+           return null;
+       if (code == HspcObservationWeightMeasMethodDevice._1964)
       return "1964";
     if (code == HspcObservationWeightMeasMethodDevice._2007)
       return "2007";
@@ -80,7 +82,7 @@ public String toCode(HspcObservationWeightMeasMethodDevice code) {
     if (code == HspcObservationWeightMeasMethodDevice._521443011)
       return "521443011";
     return "?";
-  }
+   }
 
   public String toSystem(HspcObservationWeightMeasMethodDevice code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightPrecondEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightPrecondEnumFactory.java
index 7e56d79763..4173a3b882 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightPrecondEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcObservationWeightPrecondEnumFactory.java
@@ -68,7 +68,9 @@ public HspcObservationWeightPrecond fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(HspcObservationWeightPrecond code) {
-    if (code == HspcObservationWeightPrecond._84123)
+       if (code == HspcObservationWeightPrecond.NULL)
+           return null;
+       if (code == HspcObservationWeightPrecond._84123)
       return "84123";
     if (code == HspcObservationWeightPrecond._84124)
       return "84124";
@@ -95,7 +97,7 @@ public String toCode(HspcObservationWeightPrecond code) {
     if (code == HspcObservationWeightPrecond._84137)
       return "84137";
     return "?";
-  }
+   }
 
   public String toSystem(HspcObservationWeightPrecond code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationnameuseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationnameuseEnumFactory.java
index 9f19921e08..db3b1cd28a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationnameuseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationnameuseEnumFactory.java
@@ -45,10 +45,12 @@ public HspcOrganizationOrganizationnameuse fromCode(String codeString) throws Il
   }
 
   public String toCode(HspcOrganizationOrganizationnameuse code) {
-    if (code == HspcOrganizationOrganizationnameuse._526758025)
+       if (code == HspcOrganizationOrganizationnameuse.NULL)
+           return null;
+       if (code == HspcOrganizationOrganizationnameuse._526758025)
       return "526758025";
     return "?";
-  }
+   }
 
   public String toSystem(HspcOrganizationOrganizationnameuse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationtypeEnumFactory.java
index d2d4f87ab9..43cddd5553 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcOrganizationOrganizationtypeEnumFactory.java
@@ -72,7 +72,9 @@ public HspcOrganizationOrganizationtype fromCode(String codeString) throws Illeg
   }
 
   public String toCode(HspcOrganizationOrganizationtype code) {
-    if (code == HspcOrganizationOrganizationtype._526758010)
+       if (code == HspcOrganizationOrganizationtype.NULL)
+           return null;
+       if (code == HspcOrganizationOrganizationtype._526758010)
       return "526758010";
     if (code == HspcOrganizationOrganizationtype._526758011)
       return "526758011";
@@ -103,7 +105,7 @@ public String toCode(HspcOrganizationOrganizationtype code) {
     if (code == HspcOrganizationOrganizationtype._526758024)
       return "526758024";
     return "?";
-  }
+   }
 
   public String toSystem(HspcOrganizationOrganizationtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientAdoptionInfoEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientAdoptionInfoEnumFactory.java
index 98126b2449..282f678727 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientAdoptionInfoEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientAdoptionInfoEnumFactory.java
@@ -46,12 +46,14 @@ public HspcPatientAdoptionInfo fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(HspcPatientAdoptionInfo code) {
-    if (code == HspcPatientAdoptionInfo._526742432)
+       if (code == HspcPatientAdoptionInfo.NULL)
+           return null;
+       if (code == HspcPatientAdoptionInfo._526742432)
       return "526742432";
     if (code == HspcPatientAdoptionInfo._526742433)
       return "526742433";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPatientAdoptionInfo code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientPersonNameUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientPersonNameUseEnumFactory.java
index 980038b7d9..e283916607 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientPersonNameUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientPersonNameUseEnumFactory.java
@@ -48,14 +48,16 @@ public HspcPatientPersonNameUse fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(HspcPatientPersonNameUse code) {
-    if (code == HspcPatientPersonNameUse._188)
+       if (code == HspcPatientPersonNameUse.NULL)
+           return null;
+       if (code == HspcPatientPersonNameUse._188)
       return "188";
     if (code == HspcPatientPersonNameUse._191)
       return "191";
     if (code == HspcPatientPersonNameUse._812)
       return "812";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPatientPersonNameUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientTelecomSystemEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientTelecomSystemEnumFactory.java
index dce1f08a8e..7341a0dae4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientTelecomSystemEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientTelecomSystemEnumFactory.java
@@ -48,14 +48,16 @@ public HspcPatientTelecomSystem fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(HspcPatientTelecomSystem code) {
-    if (code == HspcPatientTelecomSystem.FAX)
+       if (code == HspcPatientTelecomSystem.NULL)
+           return null;
+       if (code == HspcPatientTelecomSystem.FAX)
       return "fax";
     if (code == HspcPatientTelecomSystem.EMAIL)
       return "email";
     if (code == HspcPatientTelecomSystem.PHONE)
       return "phone";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPatientTelecomSystem code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientVeteranMilitaryStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientVeteranMilitaryStatusEnumFactory.java
index 17e67b0feb..94ceb9a0ee 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientVeteranMilitaryStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPatientVeteranMilitaryStatusEnumFactory.java
@@ -62,7 +62,9 @@ public HspcPatientVeteranMilitaryStatus fromCode(String codeString) throws Illeg
   }
 
   public String toCode(HspcPatientVeteranMilitaryStatus code) {
-    if (code == HspcPatientVeteranMilitaryStatus._8CA8CC2BBAA04CB68863418173C125D1)
+       if (code == HspcPatientVeteranMilitaryStatus.NULL)
+           return null;
+       if (code == HspcPatientVeteranMilitaryStatus._8CA8CC2BBAA04CB68863418173C125D1)
       return "8ca8cc2b-baa0-4cb6-8863-418173c125d1";
     if (code == HspcPatientVeteranMilitaryStatus._4EB9A0A1333448DF084DCEF37C9AC0D3)
       return "4eb9a0a1-3334-48df-084d-cef37c9ac0d3";
@@ -83,7 +85,7 @@ public String toCode(HspcPatientVeteranMilitaryStatus code) {
     if (code == HspcPatientVeteranMilitaryStatus._75F4440AEC3747FEB26D39C09C204676)
       return "75f4440a-ec37-47fe-b26d-39c09c204676";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPatientVeteranMilitaryStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPracticeAffiliationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPracticeAffiliationTypeEnumFactory.java
index 720d94ff5e..1bf83b89b4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPracticeAffiliationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPracticeAffiliationTypeEnumFactory.java
@@ -45,10 +45,12 @@ public HspcPractitionerPracticeAffiliationType fromCode(String codeString) throw
   }
 
   public String toCode(HspcPractitionerPracticeAffiliationType code) {
-    if (code == HspcPractitionerPracticeAffiliationType._5B595190ACEB48DEB0D68950A8829183)
+       if (code == HspcPractitionerPracticeAffiliationType.NULL)
+           return null;
+       if (code == HspcPractitionerPracticeAffiliationType._5B595190ACEB48DEB0D68950A8829183)
       return "5b595190-aceb-48de-b0d6-8950a8829183";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPractitionerPracticeAffiliationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPrivilegeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPrivilegeEnumFactory.java
index ae5b8fbaf7..dec5e8b748 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPrivilegeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerPrivilegeEnumFactory.java
@@ -52,7 +52,9 @@ public HspcPractitionerPrivilege fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(HspcPractitionerPrivilege code) {
-    if (code == HspcPractitionerPrivilege.E631014153084062A1760A03197FB489)
+       if (code == HspcPractitionerPrivilege.NULL)
+           return null;
+       if (code == HspcPractitionerPrivilege.E631014153084062A1760A03197FB489)
       return "e6310141-5308-4062-a176-0a03197fb489";
     if (code == HspcPractitionerPrivilege._0A9A9B654F9F42FAADE80D2592BDE220)
       return "0a9a9b65-4f9f-42fa-ade8-0d2592bde220";
@@ -63,7 +65,7 @@ public String toCode(HspcPractitionerPrivilege code) {
     if (code == HspcPractitionerPrivilege._45FC874FD78743F2A2AA5954446B163D)
       return "45fc874f-d787-43f2-a2aa-5954446b163d";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPractitionerPrivilege code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerTelecomSystemEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerTelecomSystemEnumFactory.java
index 7cc07d758b..4233bf5eaa 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerTelecomSystemEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcPractitionerTelecomSystemEnumFactory.java
@@ -48,14 +48,16 @@ public HspcPractitionerTelecomSystem fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(HspcPractitionerTelecomSystem code) {
-    if (code == HspcPractitionerTelecomSystem.FAX)
+       if (code == HspcPractitionerTelecomSystem.NULL)
+           return null;
+       if (code == HspcPractitionerTelecomSystem.FAX)
       return "fax";
     if (code == HspcPractitionerTelecomSystem.EMAIL)
       return "email";
     if (code == HspcPractitionerTelecomSystem.PHONE)
       return "phone";
     return "?";
-  }
+   }
 
   public String toSystem(HspcPractitionerTelecomSystem code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSpecialArrangementEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSpecialArrangementEnumFactory.java
index e48d61f9de..5d18bd195c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSpecialArrangementEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSpecialArrangementEnumFactory.java
@@ -54,7 +54,9 @@ public HspcSpecialArrangement fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(HspcSpecialArrangement code) {
-    if (code == HspcSpecialArrangement._182850)
+       if (code == HspcSpecialArrangement.NULL)
+           return null;
+       if (code == HspcSpecialArrangement._182850)
       return "182850";
     if (code == HspcSpecialArrangement._528123036)
       return "528123036";
@@ -67,7 +69,7 @@ public String toCode(HspcSpecialArrangement code) {
     if (code == HspcSpecialArrangement._528123038)
       return "528123038";
     return "?";
-  }
+   }
 
   public String toSystem(HspcSpecialArrangement code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSubstanceCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSubstanceCategoryEnumFactory.java
index e009fe2663..7e81921bc3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSubstanceCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcSubstanceCategoryEnumFactory.java
@@ -44,10 +44,12 @@ public HspcSubstanceCategory fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(HspcSubstanceCategory code) {
-    if (code == HspcSubstanceCategory._527731710)
+       if (code == HspcSubstanceCategory.NULL)
+           return null;
+       if (code == HspcSubstanceCategory._527731710)
       return "527731710";
     return "?";
-  }
+   }
 
   public String toSystem(HspcSubstanceCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcTelecomUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcTelecomUseEnumFactory.java
index 1e19ab5d08..922e3de6d7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcTelecomUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcTelecomUseEnumFactory.java
@@ -44,10 +44,12 @@ public HspcTelecomUse fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(HspcTelecomUse code) {
-    if (code == HspcTelecomUse.NS)
+       if (code == HspcTelecomUse.NULL)
+           return null;
+       if (code == HspcTelecomUse.NS)
       return "NS";
     return "?";
-  }
+   }
 
   public String toSystem(HspcTelecomUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcVitalsignassociatedprecondEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcVitalsignassociatedprecondEnumFactory.java
index cdc303dd40..8d6d665bb1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcVitalsignassociatedprecondEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HspcVitalsignassociatedprecondEnumFactory.java
@@ -50,7 +50,9 @@ public HspcVitalsignassociatedprecond fromCode(String codeString) throws Illegal
   }
 
   public String toCode(HspcVitalsignassociatedprecond code) {
-    if (code == HspcVitalsignassociatedprecond._1942)
+       if (code == HspcVitalsignassociatedprecond.NULL)
+           return null;
+       if (code == HspcVitalsignassociatedprecond._1942)
       return "1942";
     if (code == HspcVitalsignassociatedprecond._1966)
       return "1966";
@@ -59,7 +61,7 @@ public String toCode(HspcVitalsignassociatedprecond code) {
     if (code == HspcVitalsignassociatedprecond._219101)
       return "219101";
     return "?";
-  }
+   }
 
   public String toSystem(HspcVitalsignassociatedprecond code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HttpVerbEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HttpVerbEnumFactory.java
index b1052cfd31..adc979ac73 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HttpVerbEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/HttpVerbEnumFactory.java
@@ -50,7 +50,9 @@ public HttpVerb fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(HttpVerb code) {
-    if (code == HttpVerb.GET)
+       if (code == HttpVerb.NULL)
+           return null;
+       if (code == HttpVerb.GET)
       return "GET";
     if (code == HttpVerb.POST)
       return "POST";
@@ -59,7 +61,7 @@ public String toCode(HttpVerb code) {
     if (code == HttpVerb.DELETE)
       return "DELETE";
     return "?";
-  }
+   }
 
   public String toSystem(HttpVerb code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/Icd10ProceduresEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/Icd10ProceduresEnumFactory.java
index e27914cfa2..eea518168c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/Icd10ProceduresEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/Icd10ProceduresEnumFactory.java
@@ -48,14 +48,16 @@ public Icd10Procedures fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(Icd10Procedures code) {
-    if (code == Icd10Procedures._123001)
+       if (code == Icd10Procedures.NULL)
+           return null;
+       if (code == Icd10Procedures._123001)
       return "123001";
     if (code == Icd10Procedures._123002)
       return "123002";
     if (code == Icd10Procedures._123003)
       return "123003";
     return "?";
-  }
+   }
 
   public String toSystem(Icd10Procedures code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierTypeEnumFactory.java
index 985d022d53..104ef9e036 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierTypeEnumFactory.java
@@ -52,7 +52,9 @@ public IdentifierType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(IdentifierType code) {
-    if (code == IdentifierType.UDI)
+       if (code == IdentifierType.NULL)
+           return null;
+       if (code == IdentifierType.UDI)
       return "UDI";
     if (code == IdentifierType.SNO)
       return "SNO";
@@ -63,7 +65,7 @@ public String toCode(IdentifierType code) {
     if (code == IdentifierType.FILL)
       return "FILL";
     return "?";
-  }
+   }
 
   public String toSystem(IdentifierType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierUseEnumFactory.java
index 133b275993..0c447b958b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentifierUseEnumFactory.java
@@ -50,7 +50,9 @@ public IdentifierUse fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(IdentifierUse code) {
-    if (code == IdentifierUse.USUAL)
+       if (code == IdentifierUse.NULL)
+           return null;
+       if (code == IdentifierUse.USUAL)
       return "usual";
     if (code == IdentifierUse.OFFICIAL)
       return "official";
@@ -59,7 +61,7 @@ public String toCode(IdentifierUse code) {
     if (code == IdentifierUse.SECONDARY)
       return "secondary";
     return "?";
-  }
+   }
 
   public String toSystem(IdentifierUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentityAssuranceLevelEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentityAssuranceLevelEnumFactory.java
index b733ea2829..05a243f527 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentityAssuranceLevelEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IdentityAssuranceLevelEnumFactory.java
@@ -50,7 +50,9 @@ public IdentityAssuranceLevel fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(IdentityAssuranceLevel code) {
-    if (code == IdentityAssuranceLevel.LEVEL1)
+       if (code == IdentityAssuranceLevel.NULL)
+           return null;
+       if (code == IdentityAssuranceLevel.LEVEL1)
       return "level1";
     if (code == IdentityAssuranceLevel.LEVEL2)
       return "level2";
@@ -59,7 +61,7 @@ public String toCode(IdentityAssuranceLevel code) {
     if (code == IdentityAssuranceLevel.LEVEL4)
       return "level4";
     return "?";
-  }
+   }
 
   public String toSystem(IdentityAssuranceLevel code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationDateCriterionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationDateCriterionEnumFactory.java
index 22b99c3693..b5ec0f89e1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationDateCriterionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationDateCriterionEnumFactory.java
@@ -53,7 +53,9 @@ public ImmunizationRecommendationDateCriterion fromCode(String codeString) throw
   }
 
   public String toCode(ImmunizationRecommendationDateCriterion code) {
-    if (code == ImmunizationRecommendationDateCriterion.DUE)
+       if (code == ImmunizationRecommendationDateCriterion.NULL)
+           return null;
+       if (code == ImmunizationRecommendationDateCriterion.DUE)
       return "due";
     if (code == ImmunizationRecommendationDateCriterion.RECOMMENDED)
       return "recommended";
@@ -64,7 +66,7 @@ public String toCode(ImmunizationRecommendationDateCriterion code) {
     if (code == ImmunizationRecommendationDateCriterion.LATEST)
       return "latest";
     return "?";
-  }
+   }
 
   public String toSystem(ImmunizationRecommendationDateCriterion code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationStatusEnumFactory.java
index 80d95b1409..7593f80e51 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ImmunizationRecommendationStatusEnumFactory.java
@@ -46,12 +46,14 @@ public ImmunizationRecommendationStatus fromCode(String codeString) throws Illeg
   }
 
   public String toCode(ImmunizationRecommendationStatus code) {
-    if (code == ImmunizationRecommendationStatus.DUE)
+       if (code == ImmunizationRecommendationStatus.NULL)
+           return null;
+       if (code == ImmunizationRecommendationStatus.DUE)
       return "due";
     if (code == ImmunizationRecommendationStatus.OVERDUE)
       return "overdue";
     return "?";
-  }
+   }
 
   public String toSystem(ImmunizationRecommendationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/InterventionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/InterventionEnumFactory.java
index 91ecfcc919..be8471d879 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/InterventionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/InterventionEnumFactory.java
@@ -46,12 +46,14 @@ public Intervention fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(Intervention code) {
-    if (code == Intervention.UNKNOWN)
+       if (code == Intervention.NULL)
+           return null;
+       if (code == Intervention.UNKNOWN)
       return "unknown";
     if (code == Intervention.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(Intervention code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueSeverityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueSeverityEnumFactory.java
index a6915753a3..2b1f602a01 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueSeverityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueSeverityEnumFactory.java
@@ -50,7 +50,9 @@ public IssueSeverity fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(IssueSeverity code) {
-    if (code == IssueSeverity.FATAL)
+       if (code == IssueSeverity.NULL)
+           return null;
+       if (code == IssueSeverity.FATAL)
       return "fatal";
     if (code == IssueSeverity.ERROR)
       return "error";
@@ -59,7 +61,7 @@ public String toCode(IssueSeverity code) {
     if (code == IssueSeverity.INFORMATION)
       return "information";
     return "?";
-  }
+   }
 
   public String toSystem(IssueSeverity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueTypeEnumFactory.java
index 7bd063f18e..2e6e6f8b8b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/IssueTypeEnumFactory.java
@@ -100,7 +100,9 @@ public IssueType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(IssueType code) {
-    if (code == IssueType.INVALID)
+       if (code == IssueType.NULL)
+           return null;
+       if (code == IssueType.INVALID)
       return "invalid";
     if (code == IssueType.STRUCTURE)
       return "structure";
@@ -159,7 +161,7 @@ public String toCode(IssueType code) {
     if (code == IssueType.INFORMATIONAL)
       return "informational";
     return "?";
-  }
+   }
 
   public String toSystem(IssueType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ItemTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ItemTypeEnumFactory.java
index 11c52ecffb..bef0af3b42 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ItemTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ItemTypeEnumFactory.java
@@ -78,7 +78,9 @@ public ItemType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ItemType code) {
-    if (code == ItemType.GROUP)
+       if (code == ItemType.NULL)
+           return null;
+       if (code == ItemType.GROUP)
       return "group";
     if (code == ItemType.DISPLAY)
       return "display";
@@ -115,7 +117,7 @@ public String toCode(ItemType code) {
     if (code == ItemType.QUANTITY)
       return "quantity";
     return "?";
-  }
+   }
 
   public String toSystem(ItemType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480020AnswerlistEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480020AnswerlistEnumFactory.java
index 93c89b1681..03cac6a8a3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480020AnswerlistEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480020AnswerlistEnumFactory.java
@@ -56,7 +56,9 @@ public LOINC480020Answerlist fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(LOINC480020Answerlist code) {
-    if (code == LOINC480020Answerlist.LA66832)
+       if (code == LOINC480020Answerlist.NULL)
+           return null;
+       if (code == LOINC480020Answerlist.LA66832)
       return "LA6683-2";
     if (code == LOINC480020Answerlist.LA66840)
       return "LA6684-0";
@@ -71,7 +73,7 @@ public String toCode(LOINC480020Answerlist code) {
     if (code == LOINC480020Answerlist.LA181976)
       return "LA18197-6";
     return "?";
-  }
+   }
 
   public String toSystem(LOINC480020Answerlist code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480194AnswerlistEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480194AnswerlistEnumFactory.java
index 4c2a8bb6f2..006ace9d01 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480194AnswerlistEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC480194AnswerlistEnumFactory.java
@@ -56,7 +56,9 @@ public LOINC480194Answerlist fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(LOINC480194Answerlist code) {
-    if (code == LOINC480194Answerlist.LA96581)
+       if (code == LOINC480194Answerlist.NULL)
+           return null;
+       if (code == LOINC480194Answerlist.LA96581)
       return "LA9658-1";
     if (code == LOINC480194Answerlist.LA66923)
       return "LA6692-3";
@@ -71,7 +73,7 @@ public String toCode(LOINC480194Answerlist code) {
     if (code == LOINC480194Answerlist.LA66907)
       return "LA6690-7";
     return "?";
-  }
+   }
 
   public String toSystem(LOINC480194Answerlist code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC530345AnswerlistEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC530345AnswerlistEnumFactory.java
index 2cb05a0f01..6d5a5e8865 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC530345AnswerlistEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LOINC530345AnswerlistEnumFactory.java
@@ -52,7 +52,9 @@ public LOINC530345Answerlist fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(LOINC530345Answerlist code) {
-    if (code == LOINC530345Answerlist.LA67038)
+       if (code == LOINC530345Answerlist.NULL)
+           return null;
+       if (code == LOINC530345Answerlist.LA67038)
       return "LA6703-8";
     if (code == LOINC530345Answerlist.LA67046)
       return "LA6704-6";
@@ -63,7 +65,7 @@ public String toCode(LOINC530345Answerlist code) {
     if (code == LOINC530345Answerlist.LA67079)
       return "LA6707-9";
     return "?";
-  }
+   }
 
   public String toSystem(LOINC530345Answerlist code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkTypeEnumFactory.java
index 4ffab446e9..479f79fafd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkTypeEnumFactory.java
@@ -48,14 +48,16 @@ public LinkType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(LinkType code) {
-    if (code == LinkType.REPLACE)
+       if (code == LinkType.NULL)
+           return null;
+       if (code == LinkType.REPLACE)
       return "replace";
     if (code == LinkType.REFER)
       return "refer";
     if (code == LinkType.SEEALSO)
       return "seealso";
     return "?";
-  }
+   }
 
   public String toSystem(LinkType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkageTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkageTypeEnumFactory.java
index 99b90c659e..e5ea5ede18 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkageTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LinkageTypeEnumFactory.java
@@ -48,14 +48,16 @@ public LinkageType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(LinkageType code) {
-    if (code == LinkageType.SOURCE)
+       if (code == LinkageType.NULL)
+           return null;
+       if (code == LinkageType.SOURCE)
       return "source";
     if (code == LinkageType.ALTERNATE)
       return "alternate";
     if (code == LinkageType.HISTORICAL)
       return "historical";
     return "?";
-  }
+   }
 
   public String toSystem(LinkageType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListEmptyReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListEmptyReasonEnumFactory.java
index e16f69aa5a..9ba434f87d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListEmptyReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListEmptyReasonEnumFactory.java
@@ -54,7 +54,9 @@ public ListEmptyReason fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ListEmptyReason code) {
-    if (code == ListEmptyReason.NILKNOWN)
+       if (code == ListEmptyReason.NULL)
+           return null;
+       if (code == ListEmptyReason.NILKNOWN)
       return "nilknown";
     if (code == ListEmptyReason.NOTASKED)
       return "notasked";
@@ -67,7 +69,7 @@ public String toCode(ListEmptyReason code) {
     if (code == ListEmptyReason.CLOSED)
       return "closed";
     return "?";
-  }
+   }
 
   public String toSystem(ListEmptyReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListExampleCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListExampleCodesEnumFactory.java
index 51699e378e..a158656dcb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListExampleCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListExampleCodesEnumFactory.java
@@ -60,7 +60,9 @@ public ListExampleCodes fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(ListExampleCodes code) {
-    if (code == ListExampleCodes.ALERTS)
+       if (code == ListExampleCodes.NULL)
+           return null;
+       if (code == ListExampleCodes.ALERTS)
       return "alerts";
     if (code == ListExampleCodes.ADVERSERXNS)
       return "adverserxns";
@@ -79,7 +81,7 @@ public String toCode(ListExampleCodes code) {
     if (code == ListExampleCodes.PLANS)
       return "plans";
     return "?";
-  }
+   }
 
   public String toSystem(ListExampleCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListItemFlagEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListItemFlagEnumFactory.java
index b734ad28ad..6adfc671e5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListItemFlagEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListItemFlagEnumFactory.java
@@ -54,7 +54,9 @@ public ListItemFlag fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ListItemFlag code) {
-    if (code == ListItemFlag._01)
+       if (code == ListItemFlag.NULL)
+           return null;
+       if (code == ListItemFlag._01)
       return "01";
     if (code == ListItemFlag._02)
       return "02";
@@ -67,7 +69,7 @@ public String toCode(ListItemFlag code) {
     if (code == ListItemFlag._06)
       return "06";
     return "?";
-  }
+   }
 
   public String toSystem(ListItemFlag code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListModeEnumFactory.java
index af14b9422c..0518326df0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListModeEnumFactory.java
@@ -48,14 +48,16 @@ public ListMode fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ListMode code) {
-    if (code == ListMode.WORKING)
+       if (code == ListMode.NULL)
+           return null;
+       if (code == ListMode.WORKING)
       return "working";
     if (code == ListMode.SNAPSHOT)
       return "snapshot";
     if (code == ListMode.CHANGES)
       return "changes";
     return "?";
-  }
+   }
 
   public String toSystem(ListMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListOrderEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListOrderEnumFactory.java
index a07e806d12..ef9ad882f1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListOrderEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListOrderEnumFactory.java
@@ -58,7 +58,9 @@ public ListOrder fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ListOrder code) {
-    if (code == ListOrder.USER)
+       if (code == ListOrder.NULL)
+           return null;
+       if (code == ListOrder.USER)
       return "user";
     if (code == ListOrder.SYSTEM)
       return "system";
@@ -75,7 +77,7 @@ public String toCode(ListOrder code) {
     if (code == ListOrder.PATIENT)
       return "patient";
     return "?";
-  }
+   }
 
   public String toSystem(ListOrder code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListStatusEnumFactory.java
index 9548b51edf..8257b84f9b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ListStatusEnumFactory.java
@@ -48,14 +48,16 @@ public ListStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ListStatus code) {
-    if (code == ListStatus.CURRENT)
+       if (code == ListStatus.NULL)
+           return null;
+       if (code == ListStatus.CURRENT)
       return "current";
     if (code == ListStatus.RETIRED)
       return "retired";
     if (code == ListStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(ListStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationModeEnumFactory.java
index 875fb9c4d3..9a3c6a95e0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationModeEnumFactory.java
@@ -46,12 +46,14 @@ public LocationMode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(LocationMode code) {
-    if (code == LocationMode.INSTANCE)
+       if (code == LocationMode.NULL)
+           return null;
+       if (code == LocationMode.INSTANCE)
       return "instance";
     if (code == LocationMode.KIND)
       return "kind";
     return "?";
-  }
+   }
 
   public String toSystem(LocationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationPhysicalTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationPhysicalTypeEnumFactory.java
index 07d2c0f503..08517ccc61 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationPhysicalTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationPhysicalTypeEnumFactory.java
@@ -66,7 +66,9 @@ public LocationPhysicalType fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(LocationPhysicalType code) {
-    if (code == LocationPhysicalType.BU)
+       if (code == LocationPhysicalType.NULL)
+           return null;
+       if (code == LocationPhysicalType.BU)
       return "bu";
     if (code == LocationPhysicalType.WI)
       return "wi";
@@ -91,7 +93,7 @@ public String toCode(LocationPhysicalType code) {
     if (code == LocationPhysicalType.AREA)
       return "area";
     return "?";
-  }
+   }
 
   public String toSystem(LocationPhysicalType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationStatusEnumFactory.java
index 223a745304..cb8613c447 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/LocationStatusEnumFactory.java
@@ -48,14 +48,16 @@ public LocationStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(LocationStatus code) {
-    if (code == LocationStatus.ACTIVE)
+       if (code == LocationStatus.NULL)
+           return null;
+       if (code == LocationStatus.ACTIVE)
       return "active";
     if (code == LocationStatus.SUSPENDED)
       return "suspended";
     if (code == LocationStatus.INACTIVE)
       return "inactive";
     return "?";
-  }
+   }
 
   public String toSystem(LocationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapContextTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapContextTypeEnumFactory.java
index 932633d64e..76f8c7f888 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapContextTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapContextTypeEnumFactory.java
@@ -46,12 +46,14 @@ public MapContextType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(MapContextType code) {
-    if (code == MapContextType.TYPE)
+       if (code == MapContextType.NULL)
+           return null;
+       if (code == MapContextType.TYPE)
       return "type";
     if (code == MapContextType.VARIABLE)
       return "variable";
     return "?";
-  }
+   }
 
   public String toSystem(MapContextType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapInputModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapInputModeEnumFactory.java
index bf5bd391e2..102e938c6b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapInputModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapInputModeEnumFactory.java
@@ -46,12 +46,14 @@ public MapInputMode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(MapInputMode code) {
-    if (code == MapInputMode.SOURCE)
+       if (code == MapInputMode.NULL)
+           return null;
+       if (code == MapInputMode.SOURCE)
       return "source";
     if (code == MapInputMode.TARGET)
       return "target";
     return "?";
-  }
+   }
 
   public String toSystem(MapInputMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapListModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapListModeEnumFactory.java
index 75881af664..86663f8c13 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapListModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapListModeEnumFactory.java
@@ -48,14 +48,16 @@ public MapListMode fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(MapListMode code) {
-    if (code == MapListMode.FIRST)
+       if (code == MapListMode.NULL)
+           return null;
+       if (code == MapListMode.FIRST)
       return "first";
     if (code == MapListMode.SHARE)
       return "share";
     if (code == MapListMode.LAST)
       return "last";
     return "?";
-  }
+   }
 
   public String toSystem(MapListMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapModelModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapModelModeEnumFactory.java
index f4e911008d..d3df7af02e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapModelModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapModelModeEnumFactory.java
@@ -50,7 +50,9 @@ public MapModelMode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(MapModelMode code) {
-    if (code == MapModelMode.SOURCE)
+       if (code == MapModelMode.NULL)
+           return null;
+       if (code == MapModelMode.SOURCE)
       return "source";
     if (code == MapModelMode.QUERIED)
       return "queried";
@@ -59,7 +61,7 @@ public String toCode(MapModelMode code) {
     if (code == MapModelMode.PRODUCED)
       return "produced";
     return "?";
-  }
+   }
 
   public String toSystem(MapModelMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapTransformEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapTransformEnumFactory.java
index de3a380724..5d6d7b3d96 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapTransformEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MapTransformEnumFactory.java
@@ -66,7 +66,9 @@ public MapTransform fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(MapTransform code) {
-    if (code == MapTransform.CREATE)
+       if (code == MapTransform.NULL)
+           return null;
+       if (code == MapTransform.CREATE)
       return "create";
     if (code == MapTransform.COPY)
       return "copy";
@@ -91,7 +93,7 @@ public String toCode(MapTransform code) {
     if (code == MapTransform.EVALUATE)
       return "evaluate";
     return "?";
-  }
+   }
 
   public String toSystem(MapTransform code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MaritalStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MaritalStatusEnumFactory.java
index 5de6b8e6b2..001c09adbc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MaritalStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MaritalStatusEnumFactory.java
@@ -44,10 +44,12 @@ public MaritalStatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(MaritalStatus code) {
-    if (code == MaritalStatus.U)
+       if (code == MaritalStatus.NULL)
+           return null;
+       if (code == MaritalStatus.U)
       return "U";
     return "?";
-  }
+   }
 
   public String toSystem(MaritalStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MatchGradeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MatchGradeEnumFactory.java
index eab999d36b..2faaa748f3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MatchGradeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MatchGradeEnumFactory.java
@@ -50,7 +50,9 @@ public MatchGrade fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(MatchGrade code) {
-    if (code == MatchGrade.CERTAIN)
+       if (code == MatchGrade.NULL)
+           return null;
+       if (code == MatchGrade.CERTAIN)
       return "certain";
     if (code == MatchGrade.PROBABLE)
       return "probable";
@@ -59,7 +61,7 @@ public String toCode(MatchGrade code) {
     if (code == MatchGrade.CERTAINLYNOT)
       return "certainly-not";
     return "?";
-  }
+   }
 
   public String toSystem(MatchGrade code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureDataUsageEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureDataUsageEnumFactory.java
index 9d09c2c053..91e58925f6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureDataUsageEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureDataUsageEnumFactory.java
@@ -46,12 +46,14 @@ public MeasureDataUsage fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(MeasureDataUsage code) {
-    if (code == MeasureDataUsage.SUPPLEMENTALDATA)
+       if (code == MeasureDataUsage.NULL)
+           return null;
+       if (code == MeasureDataUsage.SUPPLEMENTALDATA)
       return "supplemental-data";
     if (code == MeasureDataUsage.RISKADJUSTMENTFACTOR)
       return "risk-adjustment-factor";
     return "?";
-  }
+   }
 
   public String toSystem(MeasureDataUsage code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurePopulationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurePopulationEnumFactory.java
index 2838d93dd2..535e5d0233 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurePopulationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurePopulationEnumFactory.java
@@ -60,7 +60,9 @@ public MeasurePopulation fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(MeasurePopulation code) {
-    if (code == MeasurePopulation.INITIALPOPULATION)
+       if (code == MeasurePopulation.NULL)
+           return null;
+       if (code == MeasurePopulation.INITIALPOPULATION)
       return "initial-population";
     if (code == MeasurePopulation.NUMERATOR)
       return "numerator";
@@ -79,7 +81,7 @@ public String toCode(MeasurePopulation code) {
     if (code == MeasurePopulation.MEASURESCORE)
       return "measure-score";
     return "?";
-  }
+   }
 
   public String toSystem(MeasurePopulation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportStatusEnumFactory.java
index 6c785ad5be..4589624aca 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportStatusEnumFactory.java
@@ -48,14 +48,16 @@ public MeasureReportStatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(MeasureReportStatus code) {
-    if (code == MeasureReportStatus.COMPLETE)
+       if (code == MeasureReportStatus.NULL)
+           return null;
+       if (code == MeasureReportStatus.COMPLETE)
       return "complete";
     if (code == MeasureReportStatus.PENDING)
       return "pending";
     if (code == MeasureReportStatus.ERROR)
       return "error";
     return "?";
-  }
+   }
 
   public String toSystem(MeasureReportStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportTypeEnumFactory.java
index 57810c2297..8757238a2e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureReportTypeEnumFactory.java
@@ -48,14 +48,16 @@ public MeasureReportType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(MeasureReportType code) {
-    if (code == MeasureReportType.INDIVIDUAL)
+       if (code == MeasureReportType.NULL)
+           return null;
+       if (code == MeasureReportType.INDIVIDUAL)
       return "individual";
     if (code == MeasureReportType.PATIENTLIST)
       return "patient-list";
     if (code == MeasureReportType.SUMMARY)
       return "summary";
     return "?";
-  }
+   }
 
   public String toSystem(MeasureReportType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureScoringEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureScoringEnumFactory.java
index c27a2e1693..07e6abc160 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureScoringEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureScoringEnumFactory.java
@@ -50,7 +50,9 @@ public MeasureScoring fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(MeasureScoring code) {
-    if (code == MeasureScoring.PROPORTION)
+       if (code == MeasureScoring.NULL)
+           return null;
+       if (code == MeasureScoring.PROPORTION)
       return "proportion";
     if (code == MeasureScoring.RATIO)
       return "ratio";
@@ -59,7 +61,7 @@ public String toCode(MeasureScoring code) {
     if (code == MeasureScoring.COHORT)
       return "cohort";
     return "?";
-  }
+   }
 
   public String toSystem(MeasureScoring code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureTypeEnumFactory.java
index f234aa9101..6d413ec7d6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasureTypeEnumFactory.java
@@ -46,12 +46,14 @@ public MeasureType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(MeasureType code) {
-    if (code == MeasureType.PROCESS)
+       if (code == MeasureType.NULL)
+           return null;
+       if (code == MeasureType.PROCESS)
       return "process";
     if (code == MeasureType.OUTCOME)
       return "outcome";
     return "?";
-  }
+   }
 
   public String toSystem(MeasureType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurementPrincipleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurementPrincipleEnumFactory.java
index f73b9bf39c..63dd0ea97a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurementPrincipleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MeasurementPrincipleEnumFactory.java
@@ -64,7 +64,9 @@ public MeasurementPrinciple fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(MeasurementPrinciple code) {
-    if (code == MeasurementPrinciple.OTHER)
+       if (code == MeasurementPrinciple.NULL)
+           return null;
+       if (code == MeasurementPrinciple.OTHER)
       return "other";
     if (code == MeasurementPrinciple.CHEMICAL)
       return "chemical";
@@ -87,7 +89,7 @@ public String toCode(MeasurementPrinciple code) {
     if (code == MeasurementPrinciple.MANUAL)
       return "manual";
     return "?";
-  }
+   }
 
   public String toSystem(MeasurementPrinciple code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationAdminStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationAdminStatusEnumFactory.java
index 195d7ec7a3..412f546a4b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationAdminStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationAdminStatusEnumFactory.java
@@ -52,7 +52,9 @@ public MedicationAdminStatus fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(MedicationAdminStatus code) {
-    if (code == MedicationAdminStatus.INPROGRESS)
+       if (code == MedicationAdminStatus.NULL)
+           return null;
+       if (code == MedicationAdminStatus.INPROGRESS)
       return "in-progress";
     if (code == MedicationAdminStatus.ONHOLD)
       return "on-hold";
@@ -63,7 +65,7 @@ public String toCode(MedicationAdminStatus code) {
     if (code == MedicationAdminStatus.STOPPED)
       return "stopped";
     return "?";
-  }
+   }
 
   public String toSystem(MedicationAdminStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationDispenseStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationDispenseStatusEnumFactory.java
index 03e554fb0a..0cf58a6e47 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationDispenseStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationDispenseStatusEnumFactory.java
@@ -52,7 +52,9 @@ public MedicationDispenseStatus fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(MedicationDispenseStatus code) {
-    if (code == MedicationDispenseStatus.INPROGRESS)
+       if (code == MedicationDispenseStatus.NULL)
+           return null;
+       if (code == MedicationDispenseStatus.INPROGRESS)
       return "in-progress";
     if (code == MedicationDispenseStatus.ONHOLD)
       return "on-hold";
@@ -63,7 +65,7 @@ public String toCode(MedicationDispenseStatus code) {
     if (code == MedicationDispenseStatus.STOPPED)
       return "stopped";
     return "?";
-  }
+   }
 
   public String toSystem(MedicationDispenseStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationOrderStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationOrderStatusEnumFactory.java
index 1529f774c0..b41210068c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationOrderStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationOrderStatusEnumFactory.java
@@ -54,7 +54,9 @@ public MedicationOrderStatus fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(MedicationOrderStatus code) {
-    if (code == MedicationOrderStatus.ACTIVE)
+       if (code == MedicationOrderStatus.NULL)
+           return null;
+       if (code == MedicationOrderStatus.ACTIVE)
       return "active";
     if (code == MedicationOrderStatus.ONHOLD)
       return "on-hold";
@@ -67,7 +69,7 @@ public String toCode(MedicationOrderStatus code) {
     if (code == MedicationOrderStatus.DRAFT)
       return "draft";
     return "?";
-  }
+   }
 
   public String toSystem(MedicationOrderStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationStatementStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationStatementStatusEnumFactory.java
index c354870564..9f102541dd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationStatementStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MedicationStatementStatusEnumFactory.java
@@ -50,7 +50,9 @@ public MedicationStatementStatus fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(MedicationStatementStatus code) {
-    if (code == MedicationStatementStatus.ACTIVE)
+       if (code == MedicationStatementStatus.NULL)
+           return null;
+       if (code == MedicationStatementStatus.ACTIVE)
       return "active";
     if (code == MedicationStatementStatus.COMPLETED)
       return "completed";
@@ -59,7 +61,7 @@ public String toCode(MedicationStatementStatus code) {
     if (code == MedicationStatementStatus.INTENDED)
       return "intended";
     return "?";
-  }
+   }
 
   public String toSystem(MedicationStatementStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageConformanceEventModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageConformanceEventModeEnumFactory.java
index 04b40e4627..f185b1dd42 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageConformanceEventModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageConformanceEventModeEnumFactory.java
@@ -46,12 +46,14 @@ public MessageConformanceEventMode fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(MessageConformanceEventMode code) {
-    if (code == MessageConformanceEventMode.SENDER)
+       if (code == MessageConformanceEventMode.NULL)
+           return null;
+       if (code == MessageConformanceEventMode.SENDER)
       return "sender";
     if (code == MessageConformanceEventMode.RECEIVER)
       return "receiver";
     return "?";
-  }
+   }
 
   public String toSystem(MessageConformanceEventMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageEventsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageEventsEnumFactory.java
index 8cd2f084a8..938df0cf8b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageEventsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageEventsEnumFactory.java
@@ -64,7 +64,9 @@ public MessageEvents fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(MessageEvents code) {
-    if (code == MessageEvents.CODESYSTEMEXPAND)
+       if (code == MessageEvents.NULL)
+           return null;
+       if (code == MessageEvents.CODESYSTEMEXPAND)
       return "CodeSystem-expand";
     if (code == MessageEvents.MEDICATIONADMINISTRATIONCOMPLETE)
       return "MedicationAdministration-Complete";
@@ -87,7 +89,7 @@ public String toCode(MessageEvents code) {
     if (code == MessageEvents.VALUESETEXPAND)
       return "valueset-expand";
     return "?";
-  }
+   }
 
   public String toSystem(MessageEvents code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageReasonEncounterEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageReasonEncounterEnumFactory.java
index 7f4eaf0562..886dc66f16 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageReasonEncounterEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageReasonEncounterEnumFactory.java
@@ -54,7 +54,9 @@ public MessageReasonEncounter fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(MessageReasonEncounter code) {
-    if (code == MessageReasonEncounter.ADMIT)
+       if (code == MessageReasonEncounter.NULL)
+           return null;
+       if (code == MessageReasonEncounter.ADMIT)
       return "admit";
     if (code == MessageReasonEncounter.DISCHARGE)
       return "discharge";
@@ -67,7 +69,7 @@ public String toCode(MessageReasonEncounter code) {
     if (code == MessageReasonEncounter.EDIT)
       return "edit";
     return "?";
-  }
+   }
 
   public String toSystem(MessageReasonEncounter code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageSignificanceCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageSignificanceCategoryEnumFactory.java
index 67bbb3eb5a..f3fcf5de65 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageSignificanceCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageSignificanceCategoryEnumFactory.java
@@ -48,14 +48,16 @@ public MessageSignificanceCategory fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(MessageSignificanceCategory code) {
-    if (code == MessageSignificanceCategory.CONSEQUENCE)
+       if (code == MessageSignificanceCategory.NULL)
+           return null;
+       if (code == MessageSignificanceCategory.CONSEQUENCE)
       return "Consequence";
     if (code == MessageSignificanceCategory.CURRENCY)
       return "Currency";
     if (code == MessageSignificanceCategory.NOTIFICATION)
       return "Notification";
     return "?";
-  }
+   }
 
   public String toSystem(MessageSignificanceCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageTransportEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageTransportEnumFactory.java
index 38c9b2f9c6..b0d1cd966c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageTransportEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MessageTransportEnumFactory.java
@@ -48,14 +48,16 @@ public MessageTransport fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(MessageTransport code) {
-    if (code == MessageTransport.HTTP)
+       if (code == MessageTransport.NULL)
+           return null;
+       if (code == MessageTransport.HTTP)
       return "http";
     if (code == MessageTransport.FTP)
       return "ftp";
     if (code == MessageTransport.MLLP)
       return "mllp";
     return "?";
-  }
+   }
 
   public String toSystem(MessageTransport code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationStateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationStateEnumFactory.java
index 4e2ca72e08..0a52107173 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationStateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationStateEnumFactory.java
@@ -50,7 +50,9 @@ public MetricCalibrationState fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(MetricCalibrationState code) {
-    if (code == MetricCalibrationState.NOTCALIBRATED)
+       if (code == MetricCalibrationState.NULL)
+           return null;
+       if (code == MetricCalibrationState.NOTCALIBRATED)
       return "not-calibrated";
     if (code == MetricCalibrationState.CALIBRATIONREQUIRED)
       return "calibration-required";
@@ -59,7 +61,7 @@ public String toCode(MetricCalibrationState code) {
     if (code == MetricCalibrationState.UNSPECIFIED)
       return "unspecified";
     return "?";
-  }
+   }
 
   public String toSystem(MetricCalibrationState code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationTypeEnumFactory.java
index 751598fecc..ace745c170 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCalibrationTypeEnumFactory.java
@@ -50,7 +50,9 @@ public MetricCalibrationType fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(MetricCalibrationType code) {
-    if (code == MetricCalibrationType.UNSPECIFIED)
+       if (code == MetricCalibrationType.NULL)
+           return null;
+       if (code == MetricCalibrationType.UNSPECIFIED)
       return "unspecified";
     if (code == MetricCalibrationType.OFFSET)
       return "offset";
@@ -59,7 +61,7 @@ public String toCode(MetricCalibrationType code) {
     if (code == MetricCalibrationType.TWOPOINT)
       return "two-point";
     return "?";
-  }
+   }
 
   public String toSystem(MetricCalibrationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCategoryEnumFactory.java
index 57db5b00cd..5f44bdcd96 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricCategoryEnumFactory.java
@@ -50,7 +50,9 @@ public MetricCategory fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(MetricCategory code) {
-    if (code == MetricCategory.MEASUREMENT)
+       if (code == MetricCategory.NULL)
+           return null;
+       if (code == MetricCategory.MEASUREMENT)
       return "measurement";
     if (code == MetricCategory.SETTING)
       return "setting";
@@ -59,7 +61,7 @@ public String toCode(MetricCategory code) {
     if (code == MetricCategory.UNSPECIFIED)
       return "unspecified";
     return "?";
-  }
+   }
 
   public String toSystem(MetricCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricColorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricColorEnumFactory.java
index a53face66a..5d48a0c0a3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricColorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricColorEnumFactory.java
@@ -58,7 +58,9 @@ public MetricColor fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(MetricColor code) {
-    if (code == MetricColor.BLACK)
+       if (code == MetricColor.NULL)
+           return null;
+       if (code == MetricColor.BLACK)
       return "black";
     if (code == MetricColor.RED)
       return "red";
@@ -75,7 +77,7 @@ public String toCode(MetricColor code) {
     if (code == MetricColor.WHITE)
       return "white";
     return "?";
-  }
+   }
 
   public String toSystem(MetricColor code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricOperationalStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricOperationalStatusEnumFactory.java
index 197c2cfc7c..36f23c740a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricOperationalStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MetricOperationalStatusEnumFactory.java
@@ -48,14 +48,16 @@ public MetricOperationalStatus fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(MetricOperationalStatus code) {
-    if (code == MetricOperationalStatus.ON)
+       if (code == MetricOperationalStatus.NULL)
+           return null;
+       if (code == MetricOperationalStatus.ON)
       return "on";
     if (code == MetricOperationalStatus.OFF)
       return "off";
     if (code == MetricOperationalStatus.STANDBY)
       return "standby";
     return "?";
-  }
+   }
 
   public String toSystem(MetricOperationalStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MissingToothReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MissingToothReasonEnumFactory.java
index c04da3da40..79c4d90b6e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MissingToothReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/MissingToothReasonEnumFactory.java
@@ -50,7 +50,9 @@ public MissingToothReason fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(MissingToothReason code) {
-    if (code == MissingToothReason.E)
+       if (code == MissingToothReason.NULL)
+           return null;
+       if (code == MissingToothReason.E)
       return "E";
     if (code == MissingToothReason.C)
       return "C";
@@ -59,7 +61,7 @@ public String toCode(MissingToothReason code) {
     if (code == MissingToothReason.O)
       return "O";
     return "?";
-  }
+   }
 
   public String toSystem(MissingToothReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataContributorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataContributorEnumFactory.java
index 20a08da520..aadc9d59de 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataContributorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataContributorEnumFactory.java
@@ -50,7 +50,9 @@ public ModuleMetadataContributor fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(ModuleMetadataContributor code) {
-    if (code == ModuleMetadataContributor.AUTHOR)
+       if (code == ModuleMetadataContributor.NULL)
+           return null;
+       if (code == ModuleMetadataContributor.AUTHOR)
       return "author";
     if (code == ModuleMetadataContributor.EDITOR)
       return "editor";
@@ -59,7 +61,7 @@ public String toCode(ModuleMetadataContributor code) {
     if (code == ModuleMetadataContributor.ENDORSER)
       return "endorser";
     return "?";
-  }
+   }
 
   public String toSystem(ModuleMetadataContributor code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataFocusTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataFocusTypeEnumFactory.java
index 6ba565d291..698c9be47d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataFocusTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataFocusTypeEnumFactory.java
@@ -58,7 +58,9 @@ public ModuleMetadataFocusType fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ModuleMetadataFocusType code) {
-    if (code == ModuleMetadataFocusType.PATIENTGENDER)
+       if (code == ModuleMetadataFocusType.NULL)
+           return null;
+       if (code == ModuleMetadataFocusType.PATIENTGENDER)
       return "patient-gender";
     if (code == ModuleMetadataFocusType.PATIENTAGEGROUP)
       return "patient-age-group";
@@ -75,7 +77,7 @@ public String toCode(ModuleMetadataFocusType code) {
     if (code == ModuleMetadataFocusType.JURISDICTION)
       return "jurisdiction";
     return "?";
-  }
+   }
 
   public String toSystem(ModuleMetadataFocusType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataResourceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataResourceTypeEnumFactory.java
index aa95e76553..1c0ffd5c47 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataResourceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataResourceTypeEnumFactory.java
@@ -54,7 +54,9 @@ public ModuleMetadataResourceType fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(ModuleMetadataResourceType code) {
-    if (code == ModuleMetadataResourceType.DOCUMENTATION)
+       if (code == ModuleMetadataResourceType.NULL)
+           return null;
+       if (code == ModuleMetadataResourceType.DOCUMENTATION)
       return "documentation";
     if (code == ModuleMetadataResourceType.JUSTIFICATION)
       return "justification";
@@ -67,7 +69,7 @@ public String toCode(ModuleMetadataResourceType code) {
     if (code == ModuleMetadataResourceType.DERIVEDFROM)
       return "derived-from";
     return "?";
-  }
+   }
 
   public String toSystem(ModuleMetadataResourceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataStatusEnumFactory.java
index 919836f2f1..22340bea54 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataStatusEnumFactory.java
@@ -48,14 +48,16 @@ public ModuleMetadataStatus fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(ModuleMetadataStatus code) {
-    if (code == ModuleMetadataStatus.DRAFT)
+       if (code == ModuleMetadataStatus.NULL)
+           return null;
+       if (code == ModuleMetadataStatus.DRAFT)
       return "draft";
     if (code == ModuleMetadataStatus.ACTIVE)
       return "active";
     if (code == ModuleMetadataStatus.INACTIVE)
       return "inactive";
     return "?";
-  }
+   }
 
   public String toSystem(ModuleMetadataStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataTypeEnumFactory.java
index 5583b5ed47..47b22947bb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ModuleMetadataTypeEnumFactory.java
@@ -52,7 +52,9 @@ public ModuleMetadataType fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ModuleMetadataType code) {
-    if (code == ModuleMetadataType.MODULE)
+       if (code == ModuleMetadataType.NULL)
+           return null;
+       if (code == ModuleMetadataType.MODULE)
       return "module";
     if (code == ModuleMetadataType.LIBRARY)
       return "library";
@@ -63,7 +65,7 @@ public String toCode(ModuleMetadataType code) {
     if (code == ModuleMetadataType.ORDERSET)
       return "order-set";
     return "?";
-  }
+   }
 
   public String toSystem(ModuleMetadataType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NameUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NameUseEnumFactory.java
index da9346dffd..eb17e999fe 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NameUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NameUseEnumFactory.java
@@ -56,7 +56,9 @@ public NameUse fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(NameUse code) {
-    if (code == NameUse.USUAL)
+       if (code == NameUse.NULL)
+           return null;
+       if (code == NameUse.USUAL)
       return "usual";
     if (code == NameUse.OFFICIAL)
       return "official";
@@ -71,7 +73,7 @@ public String toCode(NameUse code) {
     if (code == NameUse.MAIDEN)
       return "maiden";
     return "?";
-  }
+   }
 
   public String toSystem(NameUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemIdentifierTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemIdentifierTypeEnumFactory.java
index 8c442e90fc..b2b385eaca 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemIdentifierTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemIdentifierTypeEnumFactory.java
@@ -50,7 +50,9 @@ public NamingsystemIdentifierType fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(NamingsystemIdentifierType code) {
-    if (code == NamingsystemIdentifierType.OID)
+       if (code == NamingsystemIdentifierType.NULL)
+           return null;
+       if (code == NamingsystemIdentifierType.OID)
       return "oid";
     if (code == NamingsystemIdentifierType.UUID)
       return "uuid";
@@ -59,7 +61,7 @@ public String toCode(NamingsystemIdentifierType code) {
     if (code == NamingsystemIdentifierType.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(NamingsystemIdentifierType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemTypeEnumFactory.java
index 9b89cabd17..8711ca3652 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NamingsystemTypeEnumFactory.java
@@ -48,14 +48,16 @@ public NamingsystemType fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(NamingsystemType code) {
-    if (code == NamingsystemType.CODESYSTEM)
+       if (code == NamingsystemType.NULL)
+           return null;
+       if (code == NamingsystemType.CODESYSTEM)
       return "codesystem";
     if (code == NamingsystemType.IDENTIFIER)
       return "identifier";
     if (code == NamingsystemType.ROOT)
       return "root";
     return "?";
-  }
+   }
 
   public String toSystem(NamingsystemType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NarrativeStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NarrativeStatusEnumFactory.java
index c257effb07..5d980c565e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NarrativeStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NarrativeStatusEnumFactory.java
@@ -50,7 +50,9 @@ public NarrativeStatus fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(NarrativeStatus code) {
-    if (code == NarrativeStatus.GENERATED)
+       if (code == NarrativeStatus.NULL)
+           return null;
+       if (code == NarrativeStatus.GENERATED)
       return "generated";
     if (code == NarrativeStatus.EXTENSIONS)
       return "extensions";
@@ -59,7 +61,7 @@ public String toCode(NarrativeStatus code) {
     if (code == NarrativeStatus.EMPTY)
       return "empty";
     return "?";
-  }
+   }
 
   public String toSystem(NarrativeStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaGlobalStatementValuesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaGlobalStatementValuesEnumFactory.java
index b035cc9537..2437e55bc8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaGlobalStatementValuesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaGlobalStatementValuesEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaGlobalStatementValues fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(NehtaGlobalStatementValues code) {
-    if (code == NehtaGlobalStatementValues._01)
+       if (code == NehtaGlobalStatementValues.NULL)
+           return null;
+       if (code == NehtaGlobalStatementValues._01)
       return "01";
     if (code == NehtaGlobalStatementValues._02)
       return "02";
     if (code == NehtaGlobalStatementValues._03)
       return "03";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaGlobalStatementValues code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaImagingExaminationResultStatEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaImagingExaminationResultStatEnumFactory.java
index 3078421f1e..4f7e1ff91b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaImagingExaminationResultStatEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaImagingExaminationResultStatEnumFactory.java
@@ -52,7 +52,9 @@ public NehtaImagingExaminationResultStat fromCode(String codeString) throws Ille
   }
 
   public String toCode(NehtaImagingExaminationResultStat code) {
-    if (code == NehtaImagingExaminationResultStat._1)
+       if (code == NehtaImagingExaminationResultStat.NULL)
+           return null;
+       if (code == NehtaImagingExaminationResultStat._1)
       return "1";
     if (code == NehtaImagingExaminationResultStat._2)
       return "2";
@@ -63,7 +65,7 @@ public String toCode(NehtaImagingExaminationResultStat code) {
     if (code == NehtaImagingExaminationResultStat._5)
       return "5";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaImagingExaminationResultStat code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCancerPrimaryOrRecurrenceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCancerPrimaryOrRecurrenceEnumFactory.java
index 3d881eb44e..1cb722b43e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCancerPrimaryOrRecurrenceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCancerPrimaryOrRecurrenceEnumFactory.java
@@ -49,14 +49,16 @@ public NehtaNehtaCancerPrimaryOrRecurrence fromCode(String codeString) throws Il
   }
 
   public String toCode(NehtaNehtaCancerPrimaryOrRecurrence code) {
-    if (code == NehtaNehtaCancerPrimaryOrRecurrence.NEWPRIMARY)
+       if (code == NehtaNehtaCancerPrimaryOrRecurrence.NULL)
+           return null;
+       if (code == NehtaNehtaCancerPrimaryOrRecurrence.NEWPRIMARY)
       return "new_primary";
     if (code == NehtaNehtaCancerPrimaryOrRecurrence.LOCALRECURRENCE)
       return "local_recurrence";
     if (code == NehtaNehtaCancerPrimaryOrRecurrence.DISTANTMETASTASES)
       return "distant_metastases";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaCancerPrimaryOrRecurrence code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcOperationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcOperationTypeEnumFactory.java
index 357c49169d..ae8a63a118 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcOperationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcOperationTypeEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaCrcOperationType fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(NehtaNehtaCrcOperationType code) {
-    if (code == NehtaNehtaCrcOperationType.OTHERPROCEDURES)
+       if (code == NehtaNehtaCrcOperationType.NULL)
+           return null;
+       if (code == NehtaNehtaCrcOperationType.OTHERPROCEDURES)
       return "other_procedures";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaCrcOperationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcPeritoneumInvasionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcPeritoneumInvasionEnumFactory.java
index a4fd56a8d4..556e8972a9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcPeritoneumInvasionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcPeritoneumInvasionEnumFactory.java
@@ -46,12 +46,14 @@ public NehtaNehtaCrcPeritoneumInvasion fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaNehtaCrcPeritoneumInvasion code) {
-    if (code == NehtaNehtaCrcPeritoneumInvasion.TUMOURINVADESTOPERITONEALSURFACE)
+       if (code == NehtaNehtaCrcPeritoneumInvasion.NULL)
+           return null;
+       if (code == NehtaNehtaCrcPeritoneumInvasion.TUMOURINVADESTOPERITONEALSURFACE)
       return "tumour_invades_to_peritoneal_surface";
     if (code == NehtaNehtaCrcPeritoneumInvasion.TUMOURFORMEDNODULE_S_DISCRETEFROMTUMOURMASSALONGTHESEROSALSURFACE)
       return "tumour_formed_nodule(s)_discrete_from_tumour_mass_along_the_serosal_surface";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaCrcPeritoneumInvasion code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcRelAnteriorPeritonealReflectionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcRelAnteriorPeritonealReflectionEnumFactory.java
index 11d6f12dac..4829728dd3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcRelAnteriorPeritonealReflectionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaCrcRelAnteriorPeritonealReflectionEnumFactory.java
@@ -50,14 +50,16 @@ public NehtaNehtaCrcRelAnteriorPeritonealReflection fromCode(String codeString)
   }
 
   public String toCode(NehtaNehtaCrcRelAnteriorPeritonealReflection code) {
-    if (code == NehtaNehtaCrcRelAnteriorPeritonealReflection.ENTIRELYABOVE)
+       if (code == NehtaNehtaCrcRelAnteriorPeritonealReflection.NULL)
+           return null;
+       if (code == NehtaNehtaCrcRelAnteriorPeritonealReflection.ENTIRELYABOVE)
       return "entirely_above";
     if (code == NehtaNehtaCrcRelAnteriorPeritonealReflection.ASTRIDE)
       return "astride";
     if (code == NehtaNehtaCrcRelAnteriorPeritonealReflection.ENTIRELYBELOW)
       return "entirely_below";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaCrcRelAnteriorPeritonealReflection code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaDysplasiaEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaDysplasiaEnumFactory.java
index c817c3f735..67e5936893 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaDysplasiaEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaDysplasiaEnumFactory.java
@@ -46,12 +46,14 @@ public NehtaNehtaDysplasia fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(NehtaNehtaDysplasia code) {
-    if (code == NehtaNehtaDysplasia.WITHDYSPLASIA)
+       if (code == NehtaNehtaDysplasia.NULL)
+           return null;
+       if (code == NehtaNehtaDysplasia.WITHDYSPLASIA)
       return "with_dysplasia";
     if (code == NehtaNehtaDysplasia.WITHOUTDYSPLASIA)
       return "without_dysplasia";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaDysplasia code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaFocalNonFocalEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaFocalNonFocalEnumFactory.java
index 6612d71421..4edc598d7a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaFocalNonFocalEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaFocalNonFocalEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaFocalNonFocal fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(NehtaNehtaFocalNonFocal code) {
-    if (code == NehtaNehtaFocalNonFocal.NONFOCAL)
+       if (code == NehtaNehtaFocalNonFocal.NULL)
+           return null;
+       if (code == NehtaNehtaFocalNonFocal.NONFOCAL)
       return "non_focal";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaFocalNonFocal code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedEnumFactory.java
index 9c467a5ce2..76c35a8248 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaInvolvedNotinvolved fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(NehtaNehtaInvolvedNotinvolved code) {
-    if (code == NehtaNehtaInvolvedNotinvolved.NOTINVOLVED)
+       if (code == NehtaNehtaInvolvedNotinvolved.NULL)
+           return null;
+       if (code == NehtaNehtaInvolvedNotinvolved.NOTINVOLVED)
       return "not_involved";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaInvolvedNotinvolved code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedIndeterminateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedIndeterminateEnumFactory.java
index a046b9966a..2e2f44de6f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedIndeterminateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedIndeterminateEnumFactory.java
@@ -45,10 +45,12 @@ public NehtaNehtaInvolvedNotinvolvedIndeterminate fromCode(String codeString) th
   }
 
   public String toCode(NehtaNehtaInvolvedNotinvolvedIndeterminate code) {
-    if (code == NehtaNehtaInvolvedNotinvolvedIndeterminate.NOTINVOLVED)
+       if (code == NehtaNehtaInvolvedNotinvolvedIndeterminate.NULL)
+           return null;
+       if (code == NehtaNehtaInvolvedNotinvolvedIndeterminate.NOTINVOLVED)
       return "not_involved";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaInvolvedNotinvolvedIndeterminate code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedNaEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedNaEnumFactory.java
index f8a1eda612..fdb90c38af 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedNaEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaInvolvedNotinvolvedNaEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaInvolvedNotinvolvedNa fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaNehtaInvolvedNotinvolvedNa code) {
-    if (code == NehtaNehtaInvolvedNotinvolvedNa.NOTINVOLVED)
+       if (code == NehtaNehtaInvolvedNotinvolvedNa.NULL)
+           return null;
+       if (code == NehtaNehtaInvolvedNotinvolvedNa.NOTINVOLVED)
       return "not_involved";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaInvolvedNotinvolvedNa code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaMutatedWildtypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaMutatedWildtypeEnumFactory.java
index c0ad18ca19..5cd6eddd1b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaMutatedWildtypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaMutatedWildtypeEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaNehtaMutatedWildtype fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(NehtaNehtaMutatedWildtype code) {
-    if (code == NehtaNehtaMutatedWildtype.MUTATED)
+       if (code == NehtaNehtaMutatedWildtype.NULL)
+           return null;
+       if (code == NehtaNehtaMutatedWildtype.MUTATED)
       return "mutated";
     if (code == NehtaNehtaMutatedWildtype.WILDTYPE)
       return "wild_type";
     if (code == NehtaNehtaMutatedWildtype.NOTTESTED)
       return "not_tested";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaMutatedWildtype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNewCancerOrRecurrenceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNewCancerOrRecurrenceEnumFactory.java
index 4c6439389a..62c4d8774d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNewCancerOrRecurrenceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNewCancerOrRecurrenceEnumFactory.java
@@ -50,7 +50,9 @@ public NehtaNehtaNewCancerOrRecurrence fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaNehtaNewCancerOrRecurrence code) {
-    if (code == NehtaNehtaNewCancerOrRecurrence.NEWPRIMARY)
+       if (code == NehtaNehtaNewCancerOrRecurrence.NULL)
+           return null;
+       if (code == NehtaNehtaNewCancerOrRecurrence.NEWPRIMARY)
       return "new-primary";
     if (code == NehtaNehtaNewCancerOrRecurrence.REGIONALRECURRENCE)
       return "regional_recurrence";
@@ -59,7 +61,7 @@ public String toCode(NehtaNehtaNewCancerOrRecurrence code) {
     if (code == NehtaNehtaNewCancerOrRecurrence.INDETERMINATE)
       return "indeterminate";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaNewCancerOrRecurrence code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNoneIdentifiedPresentEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNoneIdentifiedPresentEnumFactory.java
index 671c992622..dae65c3a1b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNoneIdentifiedPresentEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNoneIdentifiedPresentEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaNoneIdentifiedPresent fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaNehtaNoneIdentifiedPresent code) {
-    if (code == NehtaNehtaNoneIdentifiedPresent.NONEIDENTIFIED)
+       if (code == NehtaNehtaNoneIdentifiedPresent.NULL)
+           return null;
+       if (code == NehtaNehtaNoneIdentifiedPresent.NONEIDENTIFIED)
       return "none_identified";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaNoneIdentifiedPresent code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentEnumFactory.java
index 318588779d..462472c9b7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaNotidentifiedPresent fromCode(String codeString) throws Illegal
   }
 
   public String toCode(NehtaNehtaNotidentifiedPresent code) {
-    if (code == NehtaNehtaNotidentifiedPresent.NOTIDENTIFIED)
+       if (code == NehtaNehtaNotidentifiedPresent.NULL)
+           return null;
+       if (code == NehtaNehtaNotidentifiedPresent.NOTIDENTIFIED)
       return "not_identified";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaNotidentifiedPresent code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentIndeterminateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentIndeterminateEnumFactory.java
index f7f61e107b..629cc7dbb2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentIndeterminateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentIndeterminateEnumFactory.java
@@ -45,10 +45,12 @@ public NehtaNehtaNotidentifiedPresentIndeterminate fromCode(String codeString) t
   }
 
   public String toCode(NehtaNehtaNotidentifiedPresentIndeterminate code) {
-    if (code == NehtaNehtaNotidentifiedPresentIndeterminate.NOTIDENTIFIED)
+       if (code == NehtaNehtaNotidentifiedPresentIndeterminate.NULL)
+           return null;
+       if (code == NehtaNehtaNotidentifiedPresentIndeterminate.NOTIDENTIFIED)
       return "not_identified";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaNotidentifiedPresentIndeterminate code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentPresentextensiveEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentPresentextensiveEnumFactory.java
index b0883d592b..6f85cd7274 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentPresentextensiveEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaNotidentifiedPresentPresentextensiveEnumFactory.java
@@ -48,12 +48,14 @@ public NehtaNehtaNotidentifiedPresentPresentextensive fromCode(String codeString
   }
 
   public String toCode(NehtaNehtaNotidentifiedPresentPresentextensive code) {
-    if (code == NehtaNehtaNotidentifiedPresentPresentextensive.NOTIDENTIFIED)
+       if (code == NehtaNehtaNotidentifiedPresentPresentextensive.NULL)
+           return null;
+       if (code == NehtaNehtaNotidentifiedPresentPresentextensive.NOTIDENTIFIED)
       return "not_identified";
     if (code == NehtaNehtaNotidentifiedPresentPresentextensive.PRESENTANDEXTENSIVE)
       return "present_and_extensive";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaNotidentifiedPresentPresentextensive code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPerforationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPerforationTypeEnumFactory.java
index f33a5f15df..4df57c673a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPerforationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPerforationTypeEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaNehtaPerforationType fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(NehtaNehtaPerforationType code) {
-    if (code == NehtaNehtaPerforationType.THROUGHTUMOURPRIORTOSURGERY)
+       if (code == NehtaNehtaPerforationType.NULL)
+           return null;
+       if (code == NehtaNehtaPerforationType.THROUGHTUMOURPRIORTOSURGERY)
       return "through_tumour_prior_to_surgery";
     if (code == NehtaNehtaPerforationType.THROUGHTUMOURDURINGSURGERYMOBILISATION)
       return "through_tumour_during_surgery_mobilisation";
     if (code == NehtaNehtaPerforationType.AWAYFROMTUMOUR)
       return "away_from_tumour";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaPerforationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPresentAbsentNsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPresentAbsentNsEnumFactory.java
index 7ce2993f92..4b01b815b4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPresentAbsentNsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaPresentAbsentNsEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaPresentAbsentNs fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(NehtaNehtaPresentAbsentNs code) {
-    if (code == NehtaNehtaPresentAbsentNs.NOTSTATED)
+       if (code == NehtaNehtaPresentAbsentNs.NULL)
+           return null;
+       if (code == NehtaNehtaPresentAbsentNs.NOTSTATED)
       return "not-stated";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaPresentAbsentNs code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadMarginPositivityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadMarginPositivityEnumFactory.java
index c3debf7530..ee748db1a9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadMarginPositivityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadMarginPositivityEnumFactory.java
@@ -45,10 +45,12 @@ public NehtaNehtaProstateRadMarginPositivity fromCode(String codeString) throws
   }
 
   public String toCode(NehtaNehtaProstateRadMarginPositivity code) {
-    if (code == NehtaNehtaProstateRadMarginPositivity.INTRAPROSTATIC)
+       if (code == NehtaNehtaProstateRadMarginPositivity.NULL)
+           return null;
+       if (code == NehtaNehtaProstateRadMarginPositivity.INTRAPROSTATIC)
       return "intraprostatic";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaProstateRadMarginPositivity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourLocationsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourLocationsEnumFactory.java
index 6e010ee3d0..ed19fb5e46 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourLocationsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourLocationsEnumFactory.java
@@ -45,10 +45,12 @@ public NehtaNehtaProstateRadTumourLocations fromCode(String codeString) throws I
   }
 
   public String toCode(NehtaNehtaProstateRadTumourLocations code) {
-    if (code == NehtaNehtaProstateRadTumourLocations.OTHER)
+       if (code == NehtaNehtaProstateRadTumourLocations.NULL)
+           return null;
+       if (code == NehtaNehtaProstateRadTumourLocations.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaProstateRadTumourLocations code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourTypeEnumFactory.java
index ddc50685cf..76830e181c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaProstateRadTumourTypeEnumFactory.java
@@ -46,12 +46,14 @@ public NehtaNehtaProstateRadTumourType fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaNehtaProstateRadTumourType code) {
-    if (code == NehtaNehtaProstateRadTumourType.ACINARVARIANT)
+       if (code == NehtaNehtaProstateRadTumourType.NULL)
+           return null;
+       if (code == NehtaNehtaProstateRadTumourType.ACINARVARIANT)
       return "acinar_variant";
     if (code == NehtaNehtaProstateRadTumourType.PROSTATICDUCTALADENOCARCINOMA)
       return "prostatic_ductal_adenocarcinoma";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaProstateRadTumourType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaReceivedNotreceivedEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaReceivedNotreceivedEnumFactory.java
index 8bc2950f70..04ed8cb573 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaReceivedNotreceivedEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaReceivedNotreceivedEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaReceivedNotreceived fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(NehtaNehtaReceivedNotreceived code) {
-    if (code == NehtaNehtaReceivedNotreceived.NOTRECEIVED)
+       if (code == NehtaNehtaReceivedNotreceived.NULL)
+           return null;
+       if (code == NehtaNehtaReceivedNotreceived.NOTRECEIVED)
       return "not_received";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaReceivedNotreceived code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResidualTumourStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResidualTumourStatusEnumFactory.java
index 4680afa050..0f80d478ea 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResidualTumourStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResidualTumourStatusEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaNehtaResidualTumourStatus fromCode(String codeString) throws Illegal
   }
 
   public String toCode(NehtaNehtaResidualTumourStatus code) {
-    if (code == NehtaNehtaResidualTumourStatus.R0)
+       if (code == NehtaNehtaResidualTumourStatus.NULL)
+           return null;
+       if (code == NehtaNehtaResidualTumourStatus.R0)
       return "r0";
     if (code == NehtaNehtaResidualTumourStatus.R1)
       return "r1";
     if (code == NehtaNehtaResidualTumourStatus.R2)
       return "r2";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaResidualTumourStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResponseToNeoadjuvantTherapyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResponseToNeoadjuvantTherapyEnumFactory.java
index 746c7f21a3..bec0885726 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResponseToNeoadjuvantTherapyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaResponseToNeoadjuvantTherapyEnumFactory.java
@@ -45,10 +45,12 @@ public NehtaNehtaResponseToNeoadjuvantTherapy fromCode(String codeString) throws
   }
 
   public String toCode(NehtaNehtaResponseToNeoadjuvantTherapy code) {
-    if (code == NehtaNehtaResponseToNeoadjuvantTherapy.NOPRIORTREATMENT)
+       if (code == NehtaNehtaResponseToNeoadjuvantTherapy.NULL)
+           return null;
+       if (code == NehtaNehtaResponseToNeoadjuvantTherapy.NOPRIORTREATMENT)
       return "no_prior_treatment";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaResponseToNeoadjuvantTherapy code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaStainTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaStainTypeEnumFactory.java
index b47f343259..375ee9ecb4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaStainTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaStainTypeEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaNehtaStainType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(NehtaNehtaStainType code) {
-    if (code == NehtaNehtaStainType.NOTTESTED)
+       if (code == NehtaNehtaStainType.NULL)
+           return null;
+       if (code == NehtaNehtaStainType.NOTTESTED)
       return "not_tested";
     if (code == NehtaNehtaStainType.NORMALSTAINING)
       return "normal_staining";
     if (code == NehtaNehtaStainType.LOSSOFSTAINING)
       return "loss_of_staining";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaStainType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaUnstableStableEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaUnstableStableEnumFactory.java
index 7940c88fd3..f6e50b098b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaUnstableStableEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaUnstableStableEnumFactory.java
@@ -48,14 +48,16 @@ public NehtaNehtaUnstableStable fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(NehtaNehtaUnstableStable code) {
-    if (code == NehtaNehtaUnstableStable.UNSTABLE)
+       if (code == NehtaNehtaUnstableStable.NULL)
+           return null;
+       if (code == NehtaNehtaUnstableStable.UNSTABLE)
       return "unstable";
     if (code == NehtaNehtaUnstableStable.STABLE)
       return "stable";
     if (code == NehtaNehtaUnstableStable.NOTTESTED)
       return "not_tested";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaUnstableStable code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaYesNoNsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaYesNoNsEnumFactory.java
index 29b4ef303d..aa0dad2f2f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaYesNoNsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaNehtaYesNoNsEnumFactory.java
@@ -44,10 +44,12 @@ public NehtaNehtaYesNoNs fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(NehtaNehtaYesNoNs code) {
-    if (code == NehtaNehtaYesNoNs.NOTSTATED)
+       if (code == NehtaNehtaYesNoNs.NULL)
+           return null;
+       if (code == NehtaNehtaYesNoNs.NOTSTATED)
       return "not-stated";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaNehtaYesNoNs code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaPathologyTestResultStatusVaEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaPathologyTestResultStatusVaEnumFactory.java
index 6da887a930..932b9139dd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaPathologyTestResultStatusVaEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaPathologyTestResultStatusVaEnumFactory.java
@@ -52,7 +52,9 @@ public NehtaPathologyTestResultStatusVa fromCode(String codeString) throws Illeg
   }
 
   public String toCode(NehtaPathologyTestResultStatusVa code) {
-    if (code == NehtaPathologyTestResultStatusVa._1)
+       if (code == NehtaPathologyTestResultStatusVa.NULL)
+           return null;
+       if (code == NehtaPathologyTestResultStatusVa._1)
       return "1";
     if (code == NehtaPathologyTestResultStatusVa._2)
       return "2";
@@ -63,7 +65,7 @@ public String toCode(NehtaPathologyTestResultStatusVa code) {
     if (code == NehtaPathologyTestResultStatusVa._5)
       return "5";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaPathologyTestResultStatusVa code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaServiceBookingStatusValuesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaServiceBookingStatusValuesEnumFactory.java
index ed65bc1668..103ec5451c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaServiceBookingStatusValuesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaServiceBookingStatusValuesEnumFactory.java
@@ -56,7 +56,9 @@ public NehtaServiceBookingStatusValues fromCode(String codeString) throws Illega
   }
 
   public String toCode(NehtaServiceBookingStatusValues code) {
-    if (code == NehtaServiceBookingStatusValues.APT)
+       if (code == NehtaServiceBookingStatusValues.NULL)
+           return null;
+       if (code == NehtaServiceBookingStatusValues.APT)
       return "APT";
     if (code == NehtaServiceBookingStatusValues.ARQ)
       return "ARQ";
@@ -71,7 +73,7 @@ public String toCode(NehtaServiceBookingStatusValues code) {
     if (code == NehtaServiceBookingStatusValues.RQO)
       return "RQO";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaServiceBookingStatusValues code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourStageGroupingEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourStageGroupingEnumFactory.java
index a8b0b31969..6e116276df 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourStageGroupingEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourStageGroupingEnumFactory.java
@@ -62,7 +62,9 @@ public NehtaTumourStageGrouping fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(NehtaTumourStageGrouping code) {
-    if (code == NehtaTumourStageGrouping._0)
+       if (code == NehtaTumourStageGrouping.NULL)
+           return null;
+       if (code == NehtaTumourStageGrouping._0)
       return "0";
     if (code == NehtaTumourStageGrouping.I)
       return "i";
@@ -83,7 +85,7 @@ public String toCode(NehtaTumourStageGrouping code) {
     if (code == NehtaTumourStageGrouping.IVB)
       return "ivb";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaTumourStageGrouping code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourTypeEnumFactory.java
index f13e9a3e24..cdb152d0be 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NehtaTumourTypeEnumFactory.java
@@ -46,12 +46,14 @@ public NehtaTumourType fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(NehtaTumourType code) {
-    if (code == NehtaTumourType.EPITHELIALTUMOURS)
+       if (code == NehtaTumourType.NULL)
+           return null;
+       if (code == NehtaTumourType.EPITHELIALTUMOURS)
       return "epithelial-tumours";
     if (code == NehtaTumourType.MESENCHYMALTUMOURS)
       return "mesenchymal-tumours";
     return "?";
-  }
+   }
 
   public String toSystem(NehtaTumourType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NetworkTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NetworkTypeEnumFactory.java
index 378dcb85ed..f91a864c18 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NetworkTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NetworkTypeEnumFactory.java
@@ -52,7 +52,9 @@ public NetworkType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(NetworkType code) {
-    if (code == NetworkType._1)
+       if (code == NetworkType.NULL)
+           return null;
+       if (code == NetworkType._1)
       return "1";
     if (code == NetworkType._2)
       return "2";
@@ -63,7 +65,7 @@ public String toCode(NetworkType code) {
     if (code == NetworkType._5)
       return "5";
     return "?";
-  }
+   }
 
   public String toSystem(NetworkType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NoteTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NoteTypeEnumFactory.java
index 2458db1d1d..c1a22621a0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NoteTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NoteTypeEnumFactory.java
@@ -48,14 +48,16 @@ public NoteType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(NoteType code) {
-    if (code == NoteType.DISPLAY)
+       if (code == NoteType.NULL)
+           return null;
+       if (code == NoteType.DISPLAY)
       return "display";
     if (code == NoteType.PRINT)
       return "print";
     if (code == NoteType.PRINTOPER)
       return "printoper";
     return "?";
-  }
+   }
 
   public String toSystem(NoteType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NutritionOrderStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NutritionOrderStatusEnumFactory.java
index 2e96484f07..22ef0dd2eb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NutritionOrderStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/NutritionOrderStatusEnumFactory.java
@@ -60,7 +60,9 @@ public NutritionOrderStatus fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(NutritionOrderStatus code) {
-    if (code == NutritionOrderStatus.PROPOSED)
+       if (code == NutritionOrderStatus.NULL)
+           return null;
+       if (code == NutritionOrderStatus.PROPOSED)
       return "proposed";
     if (code == NutritionOrderStatus.DRAFT)
       return "draft";
@@ -79,7 +81,7 @@ public String toCode(NutritionOrderStatus code) {
     if (code == NutritionOrderStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(NutritionOrderStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectLifecycleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectLifecycleEnumFactory.java
index d091d57b51..6fab3fa4b2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectLifecycleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectLifecycleEnumFactory.java
@@ -72,7 +72,9 @@ public ObjectLifecycle fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ObjectLifecycle code) {
-    if (code == ObjectLifecycle._1)
+       if (code == ObjectLifecycle.NULL)
+           return null;
+       if (code == ObjectLifecycle._1)
       return "1";
     if (code == ObjectLifecycle._2)
       return "2";
@@ -103,7 +105,7 @@ public String toCode(ObjectLifecycle code) {
     if (code == ObjectLifecycle._15)
       return "15";
     return "?";
-  }
+   }
 
   public String toSystem(ObjectLifecycle code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectRoleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectRoleEnumFactory.java
index 6fa9288b3e..06e05642fd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectRoleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectRoleEnumFactory.java
@@ -90,7 +90,9 @@ public ObjectRole fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ObjectRole code) {
-    if (code == ObjectRole._1)
+       if (code == ObjectRole.NULL)
+           return null;
+       if (code == ObjectRole._1)
       return "1";
     if (code == ObjectRole._2)
       return "2";
@@ -139,7 +141,7 @@ public String toCode(ObjectRole code) {
     if (code == ObjectRole._24)
       return "24";
     return "?";
-  }
+   }
 
   public String toSystem(ObjectRole code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectTypeEnumFactory.java
index 4d285f4c60..1c2560c80c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObjectTypeEnumFactory.java
@@ -50,7 +50,9 @@ public ObjectType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ObjectType code) {
-    if (code == ObjectType._1)
+       if (code == ObjectType.NULL)
+           return null;
+       if (code == ObjectType._1)
       return "1";
     if (code == ObjectType._2)
       return "2";
@@ -59,7 +61,7 @@ public String toCode(ObjectType code) {
     if (code == ObjectType._4)
       return "4";
     return "?";
-  }
+   }
 
   public String toSystem(ObjectType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationCategoryEnumFactory.java
index 56bc2d2acd..6a0adfa18c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationCategoryEnumFactory.java
@@ -58,7 +58,9 @@ public ObservationCategory fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(ObservationCategory code) {
-    if (code == ObservationCategory.SOCIALHISTORY)
+       if (code == ObservationCategory.NULL)
+           return null;
+       if (code == ObservationCategory.SOCIALHISTORY)
       return "social-history";
     if (code == ObservationCategory.VITALSIGNS)
       return "vital-signs";
@@ -75,7 +77,7 @@ public String toCode(ObservationCategory code) {
     if (code == ObservationCategory.THERAPY)
       return "therapy";
     return "?";
-  }
+   }
 
   public String toSystem(ObservationCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationRelationshiptypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationRelationshiptypesEnumFactory.java
index fe922e8592..ee97bd9ce8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationRelationshiptypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationRelationshiptypesEnumFactory.java
@@ -54,7 +54,9 @@ public ObservationRelationshiptypes fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(ObservationRelationshiptypes code) {
-    if (code == ObservationRelationshiptypes.HASMEMBER)
+       if (code == ObservationRelationshiptypes.NULL)
+           return null;
+       if (code == ObservationRelationshiptypes.HASMEMBER)
       return "has-member";
     if (code == ObservationRelationshiptypes.DERIVEDFROM)
       return "derived-from";
@@ -67,7 +69,7 @@ public String toCode(ObservationRelationshiptypes code) {
     if (code == ObservationRelationshiptypes.INTERFEREDBY)
       return "interfered-by";
     return "?";
-  }
+   }
 
   public String toSystem(ObservationRelationshiptypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationStatusEnumFactory.java
index c341d348b6..23214035e3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ObservationStatusEnumFactory.java
@@ -56,7 +56,9 @@ public ObservationStatus fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(ObservationStatus code) {
-    if (code == ObservationStatus.REGISTERED)
+       if (code == ObservationStatus.NULL)
+           return null;
+       if (code == ObservationStatus.REGISTERED)
       return "registered";
     if (code == ObservationStatus.PRELIMINARY)
       return "preliminary";
@@ -71,7 +73,7 @@ public String toCode(ObservationStatus code) {
     if (code == ObservationStatus.UNKNOWN)
       return "unknown";
     return "?";
-  }
+   }
 
   public String toSystem(ObservationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceCodesEnumFactory.java
index ebe02dda2b..2dc027a571 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceCodesEnumFactory.java
@@ -46,12 +46,14 @@ public OccurrenceCodes fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(OccurrenceCodes code) {
-    if (code == OccurrenceCodes._1001)
+       if (code == OccurrenceCodes.NULL)
+           return null;
+       if (code == OccurrenceCodes._1001)
       return "1001";
     if (code == OccurrenceCodes._1002)
       return "1002";
     return "?";
-  }
+   }
 
   public String toSystem(OccurrenceCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceSpanCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceSpanCodesEnumFactory.java
index c17cf20de5..a4e9434d34 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceSpanCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OccurrenceSpanCodesEnumFactory.java
@@ -46,12 +46,14 @@ public OccurrenceSpanCodes fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(OccurrenceSpanCodes code) {
-    if (code == OccurrenceSpanCodes._1001)
+       if (code == OccurrenceSpanCodes.NULL)
+           return null;
+       if (code == OccurrenceSpanCodes._1001)
       return "1001";
     if (code == OccurrenceSpanCodes._1002)
       return "1002";
     return "?";
-  }
+   }
 
   public String toSystem(OccurrenceSpanCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationKindEnumFactory.java
index 42b12a0ec0..beb1095dd0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationKindEnumFactory.java
@@ -46,12 +46,14 @@ public OperationKind fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(OperationKind code) {
-    if (code == OperationKind.OPERATION)
+       if (code == OperationKind.NULL)
+           return null;
+       if (code == OperationKind.OPERATION)
       return "operation";
     if (code == OperationKind.QUERY)
       return "query";
     return "?";
-  }
+   }
 
   public String toSystem(OperationKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationOutcomeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationOutcomeEnumFactory.java
index 52e87c7f87..aff4362c68 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationOutcomeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationOutcomeEnumFactory.java
@@ -140,7 +140,9 @@ public OperationOutcome fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(OperationOutcome code) {
-    if (code == OperationOutcome.MSGAUTHREQUIRED)
+       if (code == OperationOutcome.NULL)
+           return null;
+       if (code == OperationOutcome.MSGAUTHREQUIRED)
       return "MSG_AUTH_REQUIRED";
     if (code == OperationOutcome.MSGBADFORMAT)
       return "MSG_BAD_FORMAT";
@@ -239,7 +241,7 @@ public String toCode(OperationOutcome code) {
     if (code == OperationOutcome.SEARCHNONE)
       return "SEARCH_NONE";
     return "?";
-  }
+   }
 
   public String toSystem(OperationOutcome code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterTypeEnumFactory.java
index fe1c1302d2..ff6ff78387 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterTypeEnumFactory.java
@@ -44,10 +44,12 @@ public OperationParameterType fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(OperationParameterType code) {
-    if (code == OperationParameterType.ANY)
+       if (code == OperationParameterType.NULL)
+           return null;
+       if (code == OperationParameterType.ANY)
       return "Any";
     return "?";
-  }
+   }
 
   public String toSystem(OperationParameterType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterUseEnumFactory.java
index 16069ae976..01fff91901 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OperationParameterUseEnumFactory.java
@@ -46,12 +46,14 @@ public OperationParameterUse fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(OperationParameterUse code) {
-    if (code == OperationParameterUse.IN)
+       if (code == OperationParameterUse.NULL)
+           return null;
+       if (code == OperationParameterUse.IN)
       return "in";
     if (code == OperationParameterUse.OUT)
       return "out";
     return "?";
-  }
+   }
 
   public String toSystem(OperationParameterUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OralProsthodonticMaterialEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OralProsthodonticMaterialEnumFactory.java
index 1915d52a1a..732af38dd0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OralProsthodonticMaterialEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OralProsthodonticMaterialEnumFactory.java
@@ -50,7 +50,9 @@ public OralProsthodonticMaterial fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(OralProsthodonticMaterial code) {
-    if (code == OralProsthodonticMaterial._1)
+       if (code == OralProsthodonticMaterial.NULL)
+           return null;
+       if (code == OralProsthodonticMaterial._1)
       return "1";
     if (code == OralProsthodonticMaterial._2)
       return "2";
@@ -59,7 +61,7 @@ public String toCode(OralProsthodonticMaterial code) {
     if (code == OralProsthodonticMaterial._4)
       return "4";
     return "?";
-  }
+   }
 
   public String toSystem(OralProsthodonticMaterial code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetItemTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetItemTypeEnumFactory.java
index db57843323..9bfc78bcb2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetItemTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetItemTypeEnumFactory.java
@@ -50,7 +50,9 @@ public OrderSetItemType fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(OrderSetItemType code) {
-    if (code == OrderSetItemType.CREATE)
+       if (code == OrderSetItemType.NULL)
+           return null;
+       if (code == OrderSetItemType.CREATE)
       return "create";
     if (code == OrderSetItemType.UPDATE)
       return "update";
@@ -59,7 +61,7 @@ public String toCode(OrderSetItemType code) {
     if (code == OrderSetItemType.FIREEVENT)
       return "fire-event";
     return "?";
-  }
+   }
 
   public String toSystem(OrderSetItemType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetParticipantEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetParticipantEnumFactory.java
index c3307fb012..d6b39c0175 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetParticipantEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderSetParticipantEnumFactory.java
@@ -50,7 +50,9 @@ public OrderSetParticipant fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(OrderSetParticipant code) {
-    if (code == OrderSetParticipant.PATIENT)
+       if (code == OrderSetParticipant.NULL)
+           return null;
+       if (code == OrderSetParticipant.PATIENT)
       return "patient";
     if (code == OrderSetParticipant.PERSON)
       return "person";
@@ -59,7 +61,7 @@ public String toCode(OrderSetParticipant code) {
     if (code == OrderSetParticipant.RELATEDPERSON)
       return "related-person";
     return "?";
-  }
+   }
 
   public String toSystem(OrderSetParticipant code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderStatusEnumFactory.java
index 860a0e70a7..80aec6753e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrderStatusEnumFactory.java
@@ -60,7 +60,9 @@ public OrderStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(OrderStatus code) {
-    if (code == OrderStatus.PENDING)
+       if (code == OrderStatus.NULL)
+           return null;
+       if (code == OrderStatus.PENDING)
       return "pending";
     if (code == OrderStatus.REVIEW)
       return "review";
@@ -79,7 +81,7 @@ public String toCode(OrderStatus code) {
     if (code == OrderStatus.COMPLETED)
       return "completed";
     return "?";
-  }
+   }
 
   public String toSystem(OrderStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrganizationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrganizationTypeEnumFactory.java
index e6b739cec2..ce4fcbb7c3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrganizationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/OrganizationTypeEnumFactory.java
@@ -64,7 +64,9 @@ public OrganizationType fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(OrganizationType code) {
-    if (code == OrganizationType.PROV)
+       if (code == OrganizationType.NULL)
+           return null;
+       if (code == OrganizationType.PROV)
       return "prov";
     if (code == OrganizationType.DEPT)
       return "dept";
@@ -87,7 +89,7 @@ public String toCode(OrganizationType code) {
     if (code == OrganizationType.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(OrganizationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantrequiredEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantrequiredEnumFactory.java
index 6577a3708a..eace4e48c2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantrequiredEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantrequiredEnumFactory.java
@@ -48,14 +48,16 @@ public Participantrequired fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(Participantrequired code) {
-    if (code == Participantrequired.REQUIRED)
+       if (code == Participantrequired.NULL)
+           return null;
+       if (code == Participantrequired.REQUIRED)
       return "required";
     if (code == Participantrequired.OPTIONAL)
       return "optional";
     if (code == Participantrequired.INFORMATIONONLY)
       return "information-only";
     return "?";
-  }
+   }
 
   public String toSystem(Participantrequired code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantstatusEnumFactory.java
index 3901dac9a7..6cdb0056bc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipantstatusEnumFactory.java
@@ -54,7 +54,9 @@ public Participantstatus fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(Participantstatus code) {
-    if (code == Participantstatus.ACCEPTED)
+       if (code == Participantstatus.NULL)
+           return null;
+       if (code == Participantstatus.ACCEPTED)
       return "accepted";
     if (code == Participantstatus.DECLINED)
       return "declined";
@@ -67,7 +69,7 @@ public String toCode(Participantstatus code) {
     if (code == Participantstatus.NEEDSACTION)
       return "needs-action";
     return "?";
-  }
+   }
 
   public String toSystem(Participantstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipationstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipationstatusEnumFactory.java
index abea6ffa58..466c1677f3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipationstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ParticipationstatusEnumFactory.java
@@ -50,7 +50,9 @@ public Participationstatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(Participationstatus code) {
-    if (code == Participationstatus.ACCEPTED)
+       if (code == Participationstatus.NULL)
+           return null;
+       if (code == Participationstatus.ACCEPTED)
       return "accepted";
     if (code == Participationstatus.DECLINED)
       return "declined";
@@ -59,7 +61,7 @@ public String toCode(Participationstatus code) {
     if (code == Participationstatus.NEEDSACTION)
       return "needs-action";
     return "?";
-  }
+   }
 
   public String toSystem(Participationstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientContactRelationshipEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientContactRelationshipEnumFactory.java
index 091dc4cbc4..163c56eafe 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientContactRelationshipEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientContactRelationshipEnumFactory.java
@@ -64,7 +64,9 @@ public PatientContactRelationship fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(PatientContactRelationship code) {
-    if (code == PatientContactRelationship.EMERGENCY)
+       if (code == PatientContactRelationship.NULL)
+           return null;
+       if (code == PatientContactRelationship.EMERGENCY)
       return "emergency";
     if (code == PatientContactRelationship.FAMILY)
       return "family";
@@ -87,7 +89,7 @@ public String toCode(PatientContactRelationship code) {
     if (code == PatientContactRelationship.PARENT)
       return "parent";
     return "?";
-  }
+   }
 
   public String toSystem(PatientContactRelationship code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientMpiMatchEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientMpiMatchEnumFactory.java
index 563c670f78..10a910a280 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientMpiMatchEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PatientMpiMatchEnumFactory.java
@@ -50,7 +50,9 @@ public PatientMpiMatch fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(PatientMpiMatch code) {
-    if (code == PatientMpiMatch.CERTAIN)
+       if (code == PatientMpiMatch.NULL)
+           return null;
+       if (code == PatientMpiMatch.CERTAIN)
       return "certain";
     if (code == PatientMpiMatch.PROBABLE)
       return "probable";
@@ -59,7 +61,7 @@ public String toCode(PatientMpiMatch code) {
     if (code == PatientMpiMatch.CERTAINLYNOT)
       return "certainly-not";
     return "?";
-  }
+   }
 
   public String toSystem(PatientMpiMatch code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PayeetypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PayeetypeEnumFactory.java
index 52e564dbee..518154d160 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PayeetypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PayeetypeEnumFactory.java
@@ -48,14 +48,16 @@ public Payeetype fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Payeetype code) {
-    if (code == Payeetype.SUBSCRIBER)
+       if (code == Payeetype.NULL)
+           return null;
+       if (code == Payeetype.SUBSCRIBER)
       return "subscriber";
     if (code == Payeetype.PROVIDER)
       return "provider";
     if (code == Payeetype.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(Payeetype code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentAdjustmentReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentAdjustmentReasonEnumFactory.java
index 3df7ccdc97..5e0cbe99ca 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentAdjustmentReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentAdjustmentReasonEnumFactory.java
@@ -46,12 +46,14 @@ public PaymentAdjustmentReason fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(PaymentAdjustmentReason code) {
-    if (code == PaymentAdjustmentReason.A001)
+       if (code == PaymentAdjustmentReason.NULL)
+           return null;
+       if (code == PaymentAdjustmentReason.A001)
       return "a001";
     if (code == PaymentAdjustmentReason.A002)
       return "a002";
     return "?";
-  }
+   }
 
   public String toSystem(PaymentAdjustmentReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentStatusEnumFactory.java
index 701fb409d7..4fc751690c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentStatusEnumFactory.java
@@ -46,12 +46,14 @@ public PaymentStatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(PaymentStatus code) {
-    if (code == PaymentStatus.PAID)
+       if (code == PaymentStatus.NULL)
+           return null;
+       if (code == PaymentStatus.PAID)
       return "paid";
     if (code == PaymentStatus.CLEARED)
       return "cleared";
     return "?";
-  }
+   }
 
   public String toSystem(PaymentStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentTypeEnumFactory.java
index 3acce705b8..0507d370f9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PaymentTypeEnumFactory.java
@@ -48,14 +48,16 @@ public PaymentType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(PaymentType code) {
-    if (code == PaymentType.PAYMENT)
+       if (code == PaymentType.NULL)
+           return null;
+       if (code == PaymentType.PAYMENT)
       return "payment";
     if (code == PaymentType.ADJUSTMENT)
       return "adjustment";
     if (code == PaymentType.ADVANCE)
       return "advance";
     return "?";
-  }
+   }
 
   public String toSystem(PaymentType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerRoleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerRoleEnumFactory.java
index c8b4f87656..316e8605c0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerRoleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerRoleEnumFactory.java
@@ -54,7 +54,9 @@ public PractitionerRole fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(PractitionerRole code) {
-    if (code == PractitionerRole.DOCTOR)
+       if (code == PractitionerRole.NULL)
+           return null;
+       if (code == PractitionerRole.DOCTOR)
       return "doctor";
     if (code == PractitionerRole.NURSE)
       return "nurse";
@@ -67,7 +69,7 @@ public String toCode(PractitionerRole code) {
     if (code == PractitionerRole.ICT)
       return "ict";
     return "?";
-  }
+   }
 
   public String toSystem(PractitionerRole code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerSpecialtyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerSpecialtyEnumFactory.java
index bacb38e26d..501e04176f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerSpecialtyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PractitionerSpecialtyEnumFactory.java
@@ -52,7 +52,9 @@ public PractitionerSpecialty fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(PractitionerSpecialty code) {
-    if (code == PractitionerSpecialty.CARDIO)
+       if (code == PractitionerSpecialty.NULL)
+           return null;
+       if (code == PractitionerSpecialty.CARDIO)
       return "cardio";
     if (code == PractitionerSpecialty.DENT)
       return "dent";
@@ -63,7 +65,7 @@ public String toCode(PractitionerSpecialty code) {
     if (code == PractitionerSpecialty.SYSARCH)
       return "sysarch";
     return "?";
-  }
+   }
 
   public String toSystem(PractitionerSpecialty code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PrecheckBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PrecheckBehaviorEnumFactory.java
index c91c775743..ae3d5df7d0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PrecheckBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PrecheckBehaviorEnumFactory.java
@@ -46,12 +46,14 @@ public PrecheckBehavior fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(PrecheckBehavior code) {
-    if (code == PrecheckBehavior.YES)
+       if (code == PrecheckBehavior.NULL)
+           return null;
+       if (code == PrecheckBehavior.YES)
       return "yes";
     if (code == PrecheckBehavior.NO)
       return "no";
     return "?";
-  }
+   }
 
   public String toSystem(PrecheckBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureProgressStatusCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureProgressStatusCodesEnumFactory.java
index 550cd4688d..944c2b277c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureProgressStatusCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureProgressStatusCodesEnumFactory.java
@@ -54,7 +54,9 @@ public ProcedureProgressStatusCodes fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(ProcedureProgressStatusCodes code) {
-    if (code == ProcedureProgressStatusCodes.A)
+       if (code == ProcedureProgressStatusCodes.NULL)
+           return null;
+       if (code == ProcedureProgressStatusCodes.A)
       return "a";
     if (code == ProcedureProgressStatusCodes.B)
       return "b";
@@ -67,7 +69,7 @@ public String toCode(ProcedureProgressStatusCodes code) {
     if (code == ProcedureProgressStatusCodes.F)
       return "f";
     return "?";
-  }
+   }
 
   public String toSystem(ProcedureProgressStatusCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRelationshipTypeEnumFactory.java
index 3dab130045..9fd42e959d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRelationshipTypeEnumFactory.java
@@ -46,12 +46,14 @@ public ProcedureRelationshipType fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(ProcedureRelationshipType code) {
-    if (code == ProcedureRelationshipType.CAUSEDBY)
+       if (code == ProcedureRelationshipType.NULL)
+           return null;
+       if (code == ProcedureRelationshipType.CAUSEDBY)
       return "caused-by";
     if (code == ProcedureRelationshipType.BECAUSEOF)
       return "because-of";
     return "?";
-  }
+   }
 
   public String toSystem(ProcedureRelationshipType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestPriorityEnumFactory.java
index d8efc9d984..6af5c3fe15 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestPriorityEnumFactory.java
@@ -50,7 +50,9 @@ public ProcedureRequestPriority fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(ProcedureRequestPriority code) {
-    if (code == ProcedureRequestPriority.ROUTINE)
+       if (code == ProcedureRequestPriority.NULL)
+           return null;
+       if (code == ProcedureRequestPriority.ROUTINE)
       return "routine";
     if (code == ProcedureRequestPriority.URGENT)
       return "urgent";
@@ -59,7 +61,7 @@ public String toCode(ProcedureRequestPriority code) {
     if (code == ProcedureRequestPriority.ASAP)
       return "asap";
     return "?";
-  }
+   }
 
   public String toSystem(ProcedureRequestPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestStatusEnumFactory.java
index f8d54b4b2a..07a8d5d672 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureRequestStatusEnumFactory.java
@@ -62,7 +62,9 @@ public ProcedureRequestStatus fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ProcedureRequestStatus code) {
-    if (code == ProcedureRequestStatus.PROPOSED)
+       if (code == ProcedureRequestStatus.NULL)
+           return null;
+       if (code == ProcedureRequestStatus.PROPOSED)
       return "proposed";
     if (code == ProcedureRequestStatus.DRAFT)
       return "draft";
@@ -83,7 +85,7 @@ public String toCode(ProcedureRequestStatus code) {
     if (code == ProcedureRequestStatus.ABORTED)
       return "aborted";
     return "?";
-  }
+   }
 
   public String toSystem(ProcedureRequestStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureStatusEnumFactory.java
index adfb8bb7c3..b12d46c228 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcedureStatusEnumFactory.java
@@ -50,7 +50,9 @@ public ProcedureStatus fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ProcedureStatus code) {
-    if (code == ProcedureStatus.INPROGRESS)
+       if (code == ProcedureStatus.NULL)
+           return null;
+       if (code == ProcedureStatus.INPROGRESS)
       return "in-progress";
     if (code == ProcedureStatus.ABORTED)
       return "aborted";
@@ -59,7 +61,7 @@ public String toCode(ProcedureStatus code) {
     if (code == ProcedureStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(ProcedureStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessOutcomeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessOutcomeEnumFactory.java
index ad3d3f6128..b05f987d49 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessOutcomeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessOutcomeEnumFactory.java
@@ -48,14 +48,16 @@ public ProcessOutcome fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ProcessOutcome code) {
-    if (code == ProcessOutcome.COMPLETE)
+       if (code == ProcessOutcome.NULL)
+           return null;
+       if (code == ProcessOutcome.COMPLETE)
       return "complete";
     if (code == ProcessOutcome.PENDED)
       return "pended";
     if (code == ProcessOutcome.ERROR)
       return "error";
     return "?";
-  }
+   }
 
   public String toSystem(ProcessOutcome code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessPriorityEnumFactory.java
index 08789399ee..dabc2b42fa 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProcessPriorityEnumFactory.java
@@ -48,14 +48,16 @@ public ProcessPriority fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ProcessPriority code) {
-    if (code == ProcessPriority.STAT)
+       if (code == ProcessPriority.NULL)
+           return null;
+       if (code == ProcessPriority.STAT)
       return "stat";
     if (code == ProcessPriority.NORMAL)
       return "normal";
     if (code == ProcessPriority.DEFERRED)
       return "deferred";
     return "?";
-  }
+   }
 
   public String toSystem(ProcessPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileDestinationTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileDestinationTypesEnumFactory.java
index 3b4c471f94..5c85ed20ae 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileDestinationTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileDestinationTypesEnumFactory.java
@@ -50,7 +50,9 @@ public ProfileDestinationTypes fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ProfileDestinationTypes code) {
-    if (code == ProfileDestinationTypes.FHIRDSTU2SERVER)
+       if (code == ProfileDestinationTypes.NULL)
+           return null;
+       if (code == ProfileDestinationTypes.FHIRDSTU2SERVER)
       return "FHIR-DSTU2-Server";
     if (code == ProfileDestinationTypes.FHIRDSTU2SDCFORMMANAGER)
       return "FHIR-DSTU2-SDC-FormManager";
@@ -59,7 +61,7 @@ public String toCode(ProfileDestinationTypes code) {
     if (code == ProfileDestinationTypes.FHIRDSTU2SDCFORMPROCESSOR)
       return "FHIR-DSTU2-SDC-FormProcessor";
     return "?";
-  }
+   }
 
   public String toSystem(ProfileDestinationTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileOriginTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileOriginTypesEnumFactory.java
index 488fa4cf9e..886b868236 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileOriginTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProfileOriginTypesEnumFactory.java
@@ -46,12 +46,14 @@ public ProfileOriginTypes fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(ProfileOriginTypes code) {
-    if (code == ProfileOriginTypes.FHIRDSTU2CLIENT)
+       if (code == ProfileOriginTypes.NULL)
+           return null;
+       if (code == ProfileOriginTypes.FHIRDSTU2CLIENT)
       return "FHIR-DSTU2-Client";
     if (code == ProfileOriginTypes.FHIRDSTU2SDCFORMFILLER)
       return "FHIR-DSTU2-SDC-FormFiller";
     return "?";
-  }
+   }
 
   public String toSystem(ProfileOriginTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PropertyRepresentationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PropertyRepresentationEnumFactory.java
index f0cebd62f7..ba01976139 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PropertyRepresentationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/PropertyRepresentationEnumFactory.java
@@ -50,7 +50,9 @@ public PropertyRepresentation fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(PropertyRepresentation code) {
-    if (code == PropertyRepresentation.XMLATTR)
+       if (code == PropertyRepresentation.NULL)
+           return null;
+       if (code == PropertyRepresentation.XMLATTR)
       return "xmlAttr";
     if (code == PropertyRepresentation.XMLTEXT)
       return "xmlText";
@@ -59,7 +61,7 @@ public String toCode(PropertyRepresentation code) {
     if (code == PropertyRepresentation.CDATEXT)
       return "cdaText";
     return "?";
-  }
+   }
 
   public String toSystem(PropertyRepresentation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolStatusEnumFactory.java
index b931fe79e2..c154d97bf0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolStatusEnumFactory.java
@@ -54,7 +54,9 @@ public ProtocolStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ProtocolStatus code) {
-    if (code == ProtocolStatus.DRAFT)
+       if (code == ProtocolStatus.NULL)
+           return null;
+       if (code == ProtocolStatus.DRAFT)
       return "draft";
     if (code == ProtocolStatus.TESTING)
       return "testing";
@@ -67,7 +69,7 @@ public String toCode(ProtocolStatus code) {
     if (code == ProtocolStatus.SUPERSEDED)
       return "superseded";
     return "?";
-  }
+   }
 
   public String toSystem(ProtocolStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolTypeEnumFactory.java
index 2b97f0b9b4..1f9d3be88c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProtocolTypeEnumFactory.java
@@ -50,7 +50,9 @@ public ProtocolType fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ProtocolType code) {
-    if (code == ProtocolType.CONDITION)
+       if (code == ProtocolType.NULL)
+           return null;
+       if (code == ProtocolType.CONDITION)
       return "condition";
     if (code == ProtocolType.DEVICE)
       return "device";
@@ -59,7 +61,7 @@ public String toCode(ProtocolType code) {
     if (code == ProtocolType.STUDY)
       return "study";
     return "?";
-  }
+   }
 
   public String toSystem(ProtocolType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentRoleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentRoleEnumFactory.java
index 686b7a45a0..b86f8f54a0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentRoleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentRoleEnumFactory.java
@@ -62,7 +62,9 @@ public ProvenanceAgentRole fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(ProvenanceAgentRole code) {
-    if (code == ProvenanceAgentRole.ENTERER)
+       if (code == ProvenanceAgentRole.NULL)
+           return null;
+       if (code == ProvenanceAgentRole.ENTERER)
       return "enterer";
     if (code == ProvenanceAgentRole.PERFORMER)
       return "performer";
@@ -83,7 +85,7 @@ public String toCode(ProvenanceAgentRole code) {
     if (code == ProvenanceAgentRole.COMPOSER)
       return "composer";
     return "?";
-  }
+   }
 
   public String toSystem(ProvenanceAgentRole code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentTypeEnumFactory.java
index 60f4e98593..905ff2c657 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceAgentTypeEnumFactory.java
@@ -56,7 +56,9 @@ public ProvenanceAgentType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(ProvenanceAgentType code) {
-    if (code == ProvenanceAgentType.PERSON)
+       if (code == ProvenanceAgentType.NULL)
+           return null;
+       if (code == ProvenanceAgentType.PERSON)
       return "person";
     if (code == ProvenanceAgentType.PRACTITIONER)
       return "practitioner";
@@ -71,7 +73,7 @@ public String toCode(ProvenanceAgentType code) {
     if (code == ProvenanceAgentType.RELATEDPERSON)
       return "related-person";
     return "?";
-  }
+   }
 
   public String toSystem(ProvenanceAgentType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceEntityRoleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceEntityRoleEnumFactory.java
index 0166820888..fec21c773d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceEntityRoleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProvenanceEntityRoleEnumFactory.java
@@ -52,7 +52,9 @@ public ProvenanceEntityRole fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(ProvenanceEntityRole code) {
-    if (code == ProvenanceEntityRole.DERIVATION)
+       if (code == ProvenanceEntityRole.NULL)
+           return null;
+       if (code == ProvenanceEntityRole.DERIVATION)
       return "derivation";
     if (code == ProvenanceEntityRole.REVISION)
       return "revision";
@@ -63,7 +65,7 @@ public String toCode(ProvenanceEntityRole code) {
     if (code == ProvenanceEntityRole.REMOVAL)
       return "removal";
     return "?";
-  }
+   }
 
   public String toSystem(ProvenanceEntityRole code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProviderQualificationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProviderQualificationEnumFactory.java
index b633294079..307b4426a0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProviderQualificationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ProviderQualificationEnumFactory.java
@@ -48,14 +48,16 @@ public ProviderQualification fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ProviderQualification code) {
-    if (code == ProviderQualification._311405)
+       if (code == ProviderQualification.NULL)
+           return null;
+       if (code == ProviderQualification._311405)
       return "311405";
     if (code == ProviderQualification._604215)
       return "604215";
     if (code == ProviderQualification._604210)
       return "604210";
     return "?";
-  }
+   }
 
   public String toSystem(ProviderQualification code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventCategoryEnumFactory.java
index eb88189ed5..2f8fcee2b7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventCategoryEnumFactory.java
@@ -62,7 +62,9 @@ public QicoreAdverseeventCategory fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(QicoreAdverseeventCategory code) {
-    if (code == QicoreAdverseeventCategory.BLOOD)
+       if (code == QicoreAdverseeventCategory.NULL)
+           return null;
+       if (code == QicoreAdverseeventCategory.BLOOD)
       return "blood";
     if (code == QicoreAdverseeventCategory.DEVICE)
       return "device";
@@ -83,7 +85,7 @@ public String toCode(QicoreAdverseeventCategory code) {
     if (code == QicoreAdverseeventCategory.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreAdverseeventCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventTypeEnumFactory.java
index 59e70748ad..bf3299b103 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAdverseeventTypeEnumFactory.java
@@ -48,14 +48,16 @@ public QicoreAdverseeventType fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(QicoreAdverseeventType code) {
-    if (code == QicoreAdverseeventType.INCIDENT)
+       if (code == QicoreAdverseeventType.NULL)
+           return null;
+       if (code == QicoreAdverseeventType.INCIDENT)
       return "incident";
     if (code == QicoreAdverseeventType.NEARMISS)
       return "near-miss";
     if (code == QicoreAdverseeventType.UNSAFE)
       return "unsafe";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreAdverseeventType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAppropriatenessScoreEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAppropriatenessScoreEnumFactory.java
index 0f751a393e..57b6a9387a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAppropriatenessScoreEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreAppropriatenessScoreEnumFactory.java
@@ -60,7 +60,9 @@ public QicoreAppropriatenessScore fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(QicoreAppropriatenessScore code) {
-    if (code == QicoreAppropriatenessScore.EXTREMELYINAPPROPRIATE)
+       if (code == QicoreAppropriatenessScore.NULL)
+           return null;
+       if (code == QicoreAppropriatenessScore.EXTREMELYINAPPROPRIATE)
       return "extremely-inappropriate";
     if (code == QicoreAppropriatenessScore.INAPPROPRIATE)
       return "inappropriate";
@@ -79,7 +81,7 @@ public String toCode(QicoreAppropriatenessScore code) {
     if (code == QicoreAppropriatenessScore.EXTREMELYAPPROPRIATE)
       return "extremely-appropriate";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreAppropriatenessScore code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreCommunicationMediumEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreCommunicationMediumEnumFactory.java
index 8ef3a06a93..b7528c3f21 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreCommunicationMediumEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreCommunicationMediumEnumFactory.java
@@ -66,7 +66,9 @@ public QicoreCommunicationMedium fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(QicoreCommunicationMedium code) {
-    if (code == QicoreCommunicationMedium.UNSPECIFIED)
+       if (code == QicoreCommunicationMedium.NULL)
+           return null;
+       if (code == QicoreCommunicationMedium.UNSPECIFIED)
       return "unspecified";
     if (code == QicoreCommunicationMedium.TELEPHONE)
       return "telephone";
@@ -91,7 +93,7 @@ public String toCode(QicoreCommunicationMedium code) {
     if (code == QicoreCommunicationMedium.PORTAL)
       return "portal";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreCommunicationMedium code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreConditionCriticalityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreConditionCriticalityEnumFactory.java
index 5d6440724d..96c8523dd8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreConditionCriticalityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreConditionCriticalityEnumFactory.java
@@ -54,7 +54,9 @@ public QicoreConditionCriticality fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(QicoreConditionCriticality code) {
-    if (code == QicoreConditionCriticality.UNSPECIFIED)
+       if (code == QicoreConditionCriticality.NULL)
+           return null;
+       if (code == QicoreConditionCriticality.UNSPECIFIED)
       return "unspecified";
     if (code == QicoreConditionCriticality.SELFRESOLVING)
       return "self-resolving";
@@ -67,7 +69,7 @@ public String toCode(QicoreConditionCriticality code) {
     if (code == QicoreConditionCriticality.REQUIRESHOSPITALIZATION)
       return "requires-hospitalization";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreConditionCriticality code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreDiagnosticorderPreconditionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreDiagnosticorderPreconditionEnumFactory.java
index b6254f8da0..ca6ca18efa 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreDiagnosticorderPreconditionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreDiagnosticorderPreconditionEnumFactory.java
@@ -48,14 +48,16 @@ public QicoreDiagnosticorderPrecondition fromCode(String codeString) throws Ille
   }
 
   public String toCode(QicoreDiagnosticorderPrecondition code) {
-    if (code == QicoreDiagnosticorderPrecondition._1)
+       if (code == QicoreDiagnosticorderPrecondition.NULL)
+           return null;
+       if (code == QicoreDiagnosticorderPrecondition._1)
       return "1";
     if (code == QicoreDiagnosticorderPrecondition._2)
       return "2";
     if (code == QicoreDiagnosticorderPrecondition._3)
       return "3";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreDiagnosticorderPrecondition code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreObservationVerificationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreObservationVerificationEnumFactory.java
index 080f2d59c3..af0a90de4e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreObservationVerificationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicoreObservationVerificationEnumFactory.java
@@ -46,12 +46,14 @@ public QicoreObservationVerification fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(QicoreObservationVerification code) {
-    if (code == QicoreObservationVerification._1)
+       if (code == QicoreObservationVerification.NULL)
+           return null;
+       if (code == QicoreObservationVerification._1)
       return "1";
     if (code == QicoreObservationVerification._2)
       return "2";
     return "?";
-  }
+   }
 
   public String toSystem(QicoreObservationVerification code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicorePatientMilitaryServiceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicorePatientMilitaryServiceEnumFactory.java
index 5f1ff282fb..fc0cf6adc9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicorePatientMilitaryServiceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QicorePatientMilitaryServiceEnumFactory.java
@@ -54,7 +54,9 @@ public QicorePatientMilitaryService fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(QicorePatientMilitaryService code) {
-    if (code == QicorePatientMilitaryService.NOTINDICATED)
+       if (code == QicorePatientMilitaryService.NULL)
+           return null;
+       if (code == QicorePatientMilitaryService.NOTINDICATED)
       return "not-indicated";
     if (code == QicorePatientMilitaryService.NOMILITARYSERVICE)
       return "no-military-service";
@@ -67,7 +69,7 @@ public String toCode(QicorePatientMilitaryService code) {
     if (code == QicorePatientMilitaryService.INACTIVERESERVE)
       return "inactive-reserve";
     return "?";
-  }
+   }
 
   public String toSystem(QicorePatientMilitaryService code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuantityComparatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuantityComparatorEnumFactory.java
index 5407c044c4..2ade66de80 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuantityComparatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuantityComparatorEnumFactory.java
@@ -50,7 +50,9 @@ public QuantityComparator fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(QuantityComparator code) {
-    if (code == QuantityComparator.LESS_THAN)
+       if (code == QuantityComparator.NULL)
+           return null;
+       if (code == QuantityComparator.LESS_THAN)
       return "<";
     if (code == QuantityComparator.LESS_OR_EQUAL)
       return "<=";
@@ -59,7 +61,7 @@ public String toCode(QuantityComparator code) {
     if (code == QuantityComparator.GREATER_THAN)
       return ">";
     return "?";
-  }
+   }
 
   public String toSystem(QuantityComparator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionMaxOccursEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionMaxOccursEnumFactory.java
index e762da695e..a87018aa5c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionMaxOccursEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionMaxOccursEnumFactory.java
@@ -44,10 +44,12 @@ public QuestionMaxOccurs fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(QuestionMaxOccurs code) {
-    if (code == QuestionMaxOccurs.ASTERISK)
+       if (code == QuestionMaxOccurs.NULL)
+           return null;
+       if (code == QuestionMaxOccurs.ASTERISK)
       return "*";
     return "?";
-  }
+   }
 
   public String toSystem(QuestionMaxOccurs code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireAnswersStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireAnswersStatusEnumFactory.java
index d86dc2cf17..9aa4fe10d0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireAnswersStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireAnswersStatusEnumFactory.java
@@ -48,14 +48,16 @@ public QuestionnaireAnswersStatus fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(QuestionnaireAnswersStatus code) {
-    if (code == QuestionnaireAnswersStatus.INPROGRESS)
+       if (code == QuestionnaireAnswersStatus.NULL)
+           return null;
+       if (code == QuestionnaireAnswersStatus.INPROGRESS)
       return "in-progress";
     if (code == QuestionnaireAnswersStatus.COMPLETED)
       return "completed";
     if (code == QuestionnaireAnswersStatus.AMENDED)
       return "amended";
     return "?";
-  }
+   }
 
   public String toSystem(QuestionnaireAnswersStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireDisplayCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireDisplayCategoryEnumFactory.java
index e9687cfcb7..407c9b9952 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireDisplayCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireDisplayCategoryEnumFactory.java
@@ -46,12 +46,14 @@ public QuestionnaireDisplayCategory fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(QuestionnaireDisplayCategory code) {
-    if (code == QuestionnaireDisplayCategory.INSTRUCTIONS)
+       if (code == QuestionnaireDisplayCategory.NULL)
+           return null;
+       if (code == QuestionnaireDisplayCategory.INSTRUCTIONS)
       return "instructions";
     if (code == QuestionnaireDisplayCategory.SECURITY)
       return "security";
     return "?";
-  }
+   }
 
   public String toSystem(QuestionnaireDisplayCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireItemControlEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireItemControlEnumFactory.java
index cfa1f4ed07..91c41449e2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireItemControlEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireItemControlEnumFactory.java
@@ -86,7 +86,9 @@ public QuestionnaireItemControl fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(QuestionnaireItemControl code) {
-    if (code == QuestionnaireItemControl.GROUP)
+       if (code == QuestionnaireItemControl.NULL)
+           return null;
+       if (code == QuestionnaireItemControl.GROUP)
       return "group";
     if (code == QuestionnaireItemControl.LIST)
       return "list";
@@ -131,7 +133,7 @@ public String toCode(QuestionnaireItemControl code) {
     if (code == QuestionnaireItemControl.TEXTBOX)
       return "text-box";
     return "?";
-  }
+   }
 
   public String toSystem(QuestionnaireItemControl code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireStatusEnumFactory.java
index eae92c0b5f..72a463203c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/QuestionnaireStatusEnumFactory.java
@@ -48,14 +48,16 @@ public QuestionnaireStatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(QuestionnaireStatus code) {
-    if (code == QuestionnaireStatus.DRAFT)
+       if (code == QuestionnaireStatus.NULL)
+           return null;
+       if (code == QuestionnaireStatus.DRAFT)
       return "draft";
     if (code == QuestionnaireStatus.PUBLISHED)
       return "published";
     if (code == QuestionnaireStatus.RETIRED)
       return "retired";
     return "?";
-  }
+   }
 
   public String toSystem(QuestionnaireStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventCertaintyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventCertaintyEnumFactory.java
index c7fd154518..7dd35bf3c7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventCertaintyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventCertaintyEnumFactory.java
@@ -48,14 +48,16 @@ public ReactionEventCertainty fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ReactionEventCertainty code) {
-    if (code == ReactionEventCertainty.UNLIKELY)
+       if (code == ReactionEventCertainty.NULL)
+           return null;
+       if (code == ReactionEventCertainty.UNLIKELY)
       return "unlikely";
     if (code == ReactionEventCertainty.LIKELY)
       return "likely";
     if (code == ReactionEventCertainty.CONFIRMED)
       return "confirmed";
     return "?";
-  }
+   }
 
   public String toSystem(ReactionEventCertainty code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventSeverityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventSeverityEnumFactory.java
index 29b401cd78..5ff84603bb 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventSeverityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReactionEventSeverityEnumFactory.java
@@ -48,14 +48,16 @@ public ReactionEventSeverity fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ReactionEventSeverity code) {
-    if (code == ReactionEventSeverity.MILD)
+       if (code == ReactionEventSeverity.NULL)
+           return null;
+       if (code == ReactionEventSeverity.MILD)
       return "mild";
     if (code == ReactionEventSeverity.MODERATE)
       return "moderate";
     if (code == ReactionEventSeverity.SEVERE)
       return "severe";
     return "?";
-  }
+   }
 
   public String toSystem(ReactionEventSeverity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationGivenCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationGivenCodesEnumFactory.java
index 853fbcdfce..a05e789d92 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationGivenCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationGivenCodesEnumFactory.java
@@ -48,14 +48,16 @@ public ReasonMedicationGivenCodes fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(ReasonMedicationGivenCodes code) {
-    if (code == ReasonMedicationGivenCodes.A)
+       if (code == ReasonMedicationGivenCodes.NULL)
+           return null;
+       if (code == ReasonMedicationGivenCodes.A)
       return "a";
     if (code == ReasonMedicationGivenCodes.B)
       return "b";
     if (code == ReasonMedicationGivenCodes.C)
       return "c";
     return "?";
-  }
+   }
 
   public String toSystem(ReasonMedicationGivenCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationNotGivenCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationNotGivenCodesEnumFactory.java
index 5a5540a87f..12ae550480 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationNotGivenCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReasonMedicationNotGivenCodesEnumFactory.java
@@ -50,7 +50,9 @@ public ReasonMedicationNotGivenCodes fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(ReasonMedicationNotGivenCodes code) {
-    if (code == ReasonMedicationNotGivenCodes.A)
+       if (code == ReasonMedicationNotGivenCodes.NULL)
+           return null;
+       if (code == ReasonMedicationNotGivenCodes.A)
       return "a";
     if (code == ReasonMedicationNotGivenCodes.B)
       return "b";
@@ -59,7 +61,7 @@ public String toCode(ReasonMedicationNotGivenCodes code) {
     if (code == ReasonMedicationNotGivenCodes.D)
       return "d";
     return "?";
-  }
+   }
 
   public String toSystem(ReasonMedicationNotGivenCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferenceVersionRulesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferenceVersionRulesEnumFactory.java
index 080f5f00a9..bf37b57d9f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferenceVersionRulesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferenceVersionRulesEnumFactory.java
@@ -48,14 +48,16 @@ public ReferenceVersionRules fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ReferenceVersionRules code) {
-    if (code == ReferenceVersionRules.EITHER)
+       if (code == ReferenceVersionRules.NULL)
+           return null;
+       if (code == ReferenceVersionRules.EITHER)
       return "either";
     if (code == ReferenceVersionRules.INDEPENDENT)
       return "independent";
     if (code == ReferenceVersionRules.SPECIFIC)
       return "specific";
     return "?";
-  }
+   }
 
   public String toSystem(ReferenceVersionRules code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferencerangeMeaningEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferencerangeMeaningEnumFactory.java
index eeb2558867..ee9cfce3a7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferencerangeMeaningEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferencerangeMeaningEnumFactory.java
@@ -68,7 +68,9 @@ public ReferencerangeMeaning fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ReferencerangeMeaning code) {
-    if (code == ReferencerangeMeaning.TYPE)
+       if (code == ReferencerangeMeaning.NULL)
+           return null;
+       if (code == ReferencerangeMeaning.TYPE)
       return "type";
     if (code == ReferencerangeMeaning.NORMAL)
       return "normal";
@@ -95,7 +97,7 @@ public String toCode(ReferencerangeMeaning code) {
     if (code == ReferencerangeMeaning.POSTMEOPAUSAL)
       return "postmeopausal";
     return "?";
-  }
+   }
 
   public String toSystem(ReferencerangeMeaning code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralcategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralcategoryEnumFactory.java
index a19ca93f6e..e3740480e5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralcategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralcategoryEnumFactory.java
@@ -48,14 +48,16 @@ public Referralcategory fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(Referralcategory code) {
-    if (code == Referralcategory.PROPOSAL)
+       if (code == Referralcategory.NULL)
+           return null;
+       if (code == Referralcategory.PROPOSAL)
       return "proposal";
     if (code == Referralcategory.PLAN)
       return "plan";
     if (code == Referralcategory.REQUEST)
       return "request";
     return "?";
-  }
+   }
 
   public String toSystem(Referralcategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralstatusEnumFactory.java
index ceff91adfb..dcf99482f6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ReferralstatusEnumFactory.java
@@ -52,7 +52,9 @@ public Referralstatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(Referralstatus code) {
-    if (code == Referralstatus.DRAFT)
+       if (code == Referralstatus.NULL)
+           return null;
+       if (code == Referralstatus.DRAFT)
       return "draft";
     if (code == Referralstatus.ACTIVE)
       return "active";
@@ -63,7 +65,7 @@ public String toCode(Referralstatus code) {
     if (code == Referralstatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(Referralstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelatedClaimRelationshipEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelatedClaimRelationshipEnumFactory.java
index f6f36d3557..43afaf554a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelatedClaimRelationshipEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelatedClaimRelationshipEnumFactory.java
@@ -46,12 +46,14 @@ public RelatedClaimRelationship fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(RelatedClaimRelationship code) {
-    if (code == RelatedClaimRelationship.PRIOR)
+       if (code == RelatedClaimRelationship.NULL)
+           return null;
+       if (code == RelatedClaimRelationship.PRIOR)
       return "prior";
     if (code == RelatedClaimRelationship.ASSOCIATED)
       return "associated";
     return "?";
-  }
+   }
 
   public String toSystem(RelatedClaimRelationship code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelationshipEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelationshipEnumFactory.java
index 2b2c0a33d0..096a150494 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelationshipEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RelationshipEnumFactory.java
@@ -52,7 +52,9 @@ public Relationship fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(Relationship code) {
-    if (code == Relationship._1)
+       if (code == Relationship.NULL)
+           return null;
+       if (code == Relationship._1)
       return "1";
     if (code == Relationship._2)
       return "2";
@@ -63,7 +65,7 @@ public String toCode(Relationship code) {
     if (code == Relationship._5)
       return "5";
     return "?";
-  }
+   }
 
   public String toSystem(Relationship code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RemittanceOutcomeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RemittanceOutcomeEnumFactory.java
index 84a027c772..27e87e7854 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RemittanceOutcomeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RemittanceOutcomeEnumFactory.java
@@ -46,12 +46,14 @@ public RemittanceOutcome fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(RemittanceOutcome code) {
-    if (code == RemittanceOutcome.COMPLETE)
+       if (code == RemittanceOutcome.NULL)
+           return null;
+       if (code == RemittanceOutcome.COMPLETE)
       return "complete";
     if (code == RemittanceOutcome.ERROR)
       return "error";
     return "?";
-  }
+   }
 
   public String toSystem(RemittanceOutcome code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RequiredBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RequiredBehaviorEnumFactory.java
index 80fbed2b14..1dfa2f051b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RequiredBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RequiredBehaviorEnumFactory.java
@@ -48,14 +48,16 @@ public RequiredBehavior fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(RequiredBehavior code) {
-    if (code == RequiredBehavior.MUST)
+       if (code == RequiredBehavior.NULL)
+           return null;
+       if (code == RequiredBehavior.MUST)
       return "must";
     if (code == RequiredBehavior.COULD)
       return "could";
     if (code == RequiredBehavior.MUSTUNLESSDOCUMENTED)
       return "must-unless-documented";
     return "?";
-  }
+   }
 
   public String toSystem(RequiredBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceAggregationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceAggregationModeEnumFactory.java
index ed6d50c7a2..2a2cf82815 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceAggregationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceAggregationModeEnumFactory.java
@@ -48,14 +48,16 @@ public ResourceAggregationMode fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(ResourceAggregationMode code) {
-    if (code == ResourceAggregationMode.CONTAINED)
+       if (code == ResourceAggregationMode.NULL)
+           return null;
+       if (code == ResourceAggregationMode.CONTAINED)
       return "contained";
     if (code == ResourceAggregationMode.REFERENCED)
       return "referenced";
     if (code == ResourceAggregationMode.BUNDLED)
       return "bundled";
     return "?";
-  }
+   }
 
   public String toSystem(ResourceAggregationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceSlicingRulesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceSlicingRulesEnumFactory.java
index 1f8ae4b3b5..0c4fe706f8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceSlicingRulesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceSlicingRulesEnumFactory.java
@@ -48,14 +48,16 @@ public ResourceSlicingRules fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(ResourceSlicingRules code) {
-    if (code == ResourceSlicingRules.CLOSED)
+       if (code == ResourceSlicingRules.NULL)
+           return null;
+       if (code == ResourceSlicingRules.CLOSED)
       return "closed";
     if (code == ResourceSlicingRules.OPEN)
       return "open";
     if (code == ResourceSlicingRules.OPENATEND)
       return "openAtEnd";
     return "?";
-  }
+   }
 
   public String toSystem(ResourceSlicingRules code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceTypesEnumFactory.java
index a3fda790bd..5a1ef2d3b2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceTypesEnumFactory.java
@@ -272,7 +272,9 @@ public ResourceTypes fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ResourceTypes code) {
-    if (code == ResourceTypes.ACCOUNT)
+       if (code == ResourceTypes.NULL)
+           return null;
+       if (code == ResourceTypes.ACCOUNT)
       return "Account";
     if (code == ResourceTypes.ALLERGYINTOLERANCE)
       return "AllergyIntolerance";
@@ -503,7 +505,7 @@ public String toCode(ResourceTypes code) {
     if (code == ResourceTypes.VISIONPRESCRIPTION)
       return "VisionPrescription";
     return "?";
-  }
+   }
 
   public String toSystem(ResourceTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceValidationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceValidationModeEnumFactory.java
index ca1dda0692..d758f73c3f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceValidationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResourceValidationModeEnumFactory.java
@@ -48,14 +48,16 @@ public ResourceValidationMode fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(ResourceValidationMode code) {
-    if (code == ResourceValidationMode.CREATE)
+       if (code == ResourceValidationMode.NULL)
+           return null;
+       if (code == ResourceValidationMode.CREATE)
       return "create";
     if (code == ResourceValidationMode.UPDATE)
       return "update";
     if (code == ResourceValidationMode.DELETE)
       return "delete";
     return "?";
-  }
+   }
 
   public String toSystem(ResourceValidationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResponseCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResponseCodeEnumFactory.java
index 321324d215..4c3fbe2e26 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResponseCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ResponseCodeEnumFactory.java
@@ -48,14 +48,16 @@ public ResponseCode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ResponseCode code) {
-    if (code == ResponseCode.OK)
+       if (code == ResponseCode.NULL)
+           return null;
+       if (code == ResponseCode.OK)
       return "ok";
     if (code == ResponseCode.TRANSIENTERROR)
       return "transient-error";
     if (code == ResponseCode.FATALERROR)
       return "fatal-error";
     return "?";
-  }
+   }
 
   public String toSystem(ResponseCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulConformanceModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulConformanceModeEnumFactory.java
index 7e5d9dfc87..7d4437704a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulConformanceModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulConformanceModeEnumFactory.java
@@ -46,12 +46,14 @@ public RestfulConformanceMode fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(RestfulConformanceMode code) {
-    if (code == RestfulConformanceMode.CLIENT)
+       if (code == RestfulConformanceMode.NULL)
+           return null;
+       if (code == RestfulConformanceMode.CLIENT)
       return "client";
     if (code == RestfulConformanceMode.SERVER)
       return "server";
     return "?";
-  }
+   }
 
   public String toSystem(RestfulConformanceMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulInteractionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulInteractionEnumFactory.java
index 8292812cd5..f126d5af75 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulInteractionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulInteractionEnumFactory.java
@@ -74,7 +74,9 @@ public RestfulInteraction fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(RestfulInteraction code) {
-    if (code == RestfulInteraction.READ)
+       if (code == RestfulInteraction.NULL)
+           return null;
+       if (code == RestfulInteraction.READ)
       return "read";
     if (code == RestfulInteraction.VREAD)
       return "vread";
@@ -107,7 +109,7 @@ public String toCode(RestfulInteraction code) {
     if (code == RestfulInteraction.OPERATION)
       return "operation";
     return "?";
-  }
+   }
 
   public String toSystem(RestfulInteraction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulSecurityServiceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulSecurityServiceEnumFactory.java
index 3e9f201ffe..7875eb1b1b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulSecurityServiceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RestfulSecurityServiceEnumFactory.java
@@ -54,7 +54,9 @@ public RestfulSecurityService fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(RestfulSecurityService code) {
-    if (code == RestfulSecurityService.OAUTH)
+       if (code == RestfulSecurityService.NULL)
+           return null;
+       if (code == RestfulSecurityService.OAUTH)
       return "OAuth";
     if (code == RestfulSecurityService.SMARTONFHIR)
       return "SMART-on-FHIR";
@@ -67,7 +69,7 @@ public String toCode(RestfulSecurityService code) {
     if (code == RestfulSecurityService.CERTIFICATES)
       return "Certificates";
     return "?";
-  }
+   }
 
   public String toSystem(RestfulSecurityService code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RiskProbabilityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RiskProbabilityEnumFactory.java
index e7faa9206e..94c6e4962b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RiskProbabilityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RiskProbabilityEnumFactory.java
@@ -52,7 +52,9 @@ public RiskProbability fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(RiskProbability code) {
-    if (code == RiskProbability.NEGLIGIBLE)
+       if (code == RiskProbability.NULL)
+           return null;
+       if (code == RiskProbability.NEGLIGIBLE)
       return "negligible";
     if (code == RiskProbability.LOW)
       return "low";
@@ -63,7 +65,7 @@ public String toCode(RiskProbability code) {
     if (code == RiskProbability.CERTAIN)
       return "certain";
     return "?";
-  }
+   }
 
   public String toSystem(RiskProbability code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RulesetEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RulesetEnumFactory.java
index ab2d16cbd3..3a2660fb23 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RulesetEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/RulesetEnumFactory.java
@@ -54,7 +54,9 @@ public Ruleset fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Ruleset code) {
-    if (code == Ruleset.X124010)
+       if (code == Ruleset.NULL)
+           return null;
+       if (code == Ruleset.X124010)
       return "x12-4010";
     if (code == Ruleset.X125010)
       return "x12-5010";
@@ -67,7 +69,7 @@ public String toCode(Ruleset code) {
     if (code == Ruleset.CPHA3)
       return "cpha-3";
     return "?";
-  }
+   }
 
   public String toSystem(Ruleset code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchEntryModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchEntryModeEnumFactory.java
index dd06eb61de..da8726f2ec 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchEntryModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchEntryModeEnumFactory.java
@@ -48,14 +48,16 @@ public SearchEntryMode fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(SearchEntryMode code) {
-    if (code == SearchEntryMode.MATCH)
+       if (code == SearchEntryMode.NULL)
+           return null;
+       if (code == SearchEntryMode.MATCH)
       return "match";
     if (code == SearchEntryMode.INCLUDE)
       return "include";
     if (code == SearchEntryMode.OUTCOME)
       return "outcome";
     return "?";
-  }
+   }
 
   public String toSystem(SearchEntryMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchModifierCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchModifierCodeEnumFactory.java
index 832953b327..349c501c2c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchModifierCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchModifierCodeEnumFactory.java
@@ -62,7 +62,9 @@ public SearchModifierCode fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(SearchModifierCode code) {
-    if (code == SearchModifierCode.MISSING)
+       if (code == SearchModifierCode.NULL)
+           return null;
+       if (code == SearchModifierCode.MISSING)
       return "missing";
     if (code == SearchModifierCode.EXACT)
       return "exact";
@@ -83,7 +85,7 @@ public String toCode(SearchModifierCode code) {
     if (code == SearchModifierCode.TYPE)
       return "type";
     return "?";
-  }
+   }
 
   public String toSystem(SearchModifierCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchParamTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchParamTypeEnumFactory.java
index 10c8704dea..f3f638efc7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchParamTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchParamTypeEnumFactory.java
@@ -58,7 +58,9 @@ public SearchParamType fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(SearchParamType code) {
-    if (code == SearchParamType.NUMBER)
+       if (code == SearchParamType.NULL)
+           return null;
+       if (code == SearchParamType.NUMBER)
       return "number";
     if (code == SearchParamType.DATE)
       return "date";
@@ -75,7 +77,7 @@ public String toCode(SearchParamType code) {
     if (code == SearchParamType.URI)
       return "uri";
     return "?";
-  }
+   }
 
   public String toSystem(SearchParamType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchXpathUsageEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchXpathUsageEnumFactory.java
index a1676cf0ec..17fba3f985 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchXpathUsageEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SearchXpathUsageEnumFactory.java
@@ -52,7 +52,9 @@ public SearchXpathUsage fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(SearchXpathUsage code) {
-    if (code == SearchXpathUsage.NORMAL)
+       if (code == SearchXpathUsage.NULL)
+           return null;
+       if (code == SearchXpathUsage.NORMAL)
       return "normal";
     if (code == SearchXpathUsage.PHONETIC)
       return "phonetic";
@@ -63,7 +65,7 @@ public String toCode(SearchXpathUsage code) {
     if (code == SearchXpathUsage.OTHER)
       return "other";
     return "?";
-  }
+   }
 
   public String toSystem(SearchXpathUsage code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SelectionBehaviorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SelectionBehaviorEnumFactory.java
index 0cac88fe98..bcacdd020e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SelectionBehaviorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SelectionBehaviorEnumFactory.java
@@ -54,7 +54,9 @@ public SelectionBehavior fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(SelectionBehavior code) {
-    if (code == SelectionBehavior.ANY)
+       if (code == SelectionBehavior.NULL)
+           return null;
+       if (code == SelectionBehavior.ANY)
       return "any";
     if (code == SelectionBehavior.ALL)
       return "all";
@@ -67,7 +69,7 @@ public String toCode(SelectionBehavior code) {
     if (code == SelectionBehavior.ONEORMORE)
       return "one-or-more";
     return "?";
-  }
+   }
 
   public String toSystem(SelectionBehavior code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SequenceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SequenceTypeEnumFactory.java
index 98057271fb..75cf4c92d0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SequenceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SequenceTypeEnumFactory.java
@@ -48,14 +48,16 @@ public SequenceType fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(SequenceType code) {
-    if (code == SequenceType.AA)
+       if (code == SequenceType.NULL)
+           return null;
+       if (code == SequenceType.AA)
       return "AA";
     if (code == SequenceType.DNA)
       return "DNA";
     if (code == SequenceType.RNA)
       return "RNA";
     return "?";
-  }
+   }
 
   public String toSystem(SequenceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceCategoryEnumFactory.java
index 38ea8f7005..1ab6d04652 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceCategoryEnumFactory.java
@@ -118,7 +118,9 @@ public ServiceCategory fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ServiceCategory code) {
-    if (code == ServiceCategory._1)
+       if (code == ServiceCategory.NULL)
+           return null;
+       if (code == ServiceCategory._1)
       return "1";
     if (code == ServiceCategory._2)
       return "2";
@@ -195,7 +197,7 @@ public String toCode(ServiceCategory code) {
     if (code == ServiceCategory._33)
       return "33";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceModifiersEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceModifiersEnumFactory.java
index 5aa26f7c81..512eb8ac13 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceModifiersEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceModifiersEnumFactory.java
@@ -46,12 +46,14 @@ public ServiceModifiers fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(ServiceModifiers code) {
-    if (code == ServiceModifiers.SR)
+       if (code == ServiceModifiers.NULL)
+           return null;
+       if (code == ServiceModifiers.SR)
       return "SR";
     if (code == ServiceModifiers.AH)
       return "AH";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceModifiers code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePharmacyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePharmacyEnumFactory.java
index b0312115d8..2a0e96cdfc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePharmacyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePharmacyEnumFactory.java
@@ -46,12 +46,14 @@ public ServicePharmacy fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(ServicePharmacy code) {
-    if (code == ServicePharmacy.SMOKECESS)
+       if (code == ServicePharmacy.NULL)
+           return null;
+       if (code == ServicePharmacy.SMOKECESS)
       return "smokecess";
     if (code == ServicePharmacy.FLUSHOT)
       return "flushot";
     return "?";
-  }
+   }
 
   public String toSystem(ServicePharmacy code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePlaceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePlaceEnumFactory.java
index bf699f125b..0729e73844 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePlaceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServicePlaceEnumFactory.java
@@ -46,12 +46,14 @@ public ServicePlace fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ServicePlace code) {
-    if (code == ServicePlace.EMERGENCY)
+       if (code == ServicePlace.NULL)
+           return null;
+       if (code == ServicePlace.EMERGENCY)
       return "emergency";
     if (code == ServicePlace.CLINIC)
       return "clinic";
     return "?";
-  }
+   }
 
   public String toSystem(ServicePlace code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProductEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProductEnumFactory.java
index c1671187e7..ddcaa0f3fe 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProductEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProductEnumFactory.java
@@ -46,12 +46,14 @@ public ServiceProduct fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(ServiceProduct code) {
-    if (code == ServiceProduct.EXAM)
+       if (code == ServiceProduct.NULL)
+           return null;
+       if (code == ServiceProduct.EXAM)
       return "exam";
     if (code == ServiceProduct.FLUSHOT)
       return "flushot";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceProduct code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProvisionConditionsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProvisionConditionsEnumFactory.java
index 5f41ff6bc4..a22715ea96 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProvisionConditionsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceProvisionConditionsEnumFactory.java
@@ -48,14 +48,16 @@ public ServiceProvisionConditions fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(ServiceProvisionConditions code) {
-    if (code == ServiceProvisionConditions.FREE)
+       if (code == ServiceProvisionConditions.NULL)
+           return null;
+       if (code == ServiceProvisionConditions.FREE)
       return "free";
     if (code == ServiceProvisionConditions.DISC)
       return "disc";
     if (code == ServiceProvisionConditions.COST)
       return "cost";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceProvisionConditions code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceReferralMethodEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceReferralMethodEnumFactory.java
index 1e91ea7d44..ba5e9a7c30 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceReferralMethodEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceReferralMethodEnumFactory.java
@@ -52,7 +52,9 @@ public ServiceReferralMethod fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(ServiceReferralMethod code) {
-    if (code == ServiceReferralMethod.FAX)
+       if (code == ServiceReferralMethod.NULL)
+           return null;
+       if (code == ServiceReferralMethod.FAX)
       return "fax";
     if (code == ServiceReferralMethod.PHONE)
       return "phone";
@@ -63,7 +65,7 @@ public String toCode(ServiceReferralMethod code) {
     if (code == ServiceReferralMethod.MAIL)
       return "mail";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceReferralMethod code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceTypeEnumFactory.java
index a0d6e18477..108f43c728 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceTypeEnumFactory.java
@@ -1234,7 +1234,9 @@ public ServiceType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ServiceType code) {
-    if (code == ServiceType._1)
+       if (code == ServiceType.NULL)
+           return null;
+       if (code == ServiceType._1)
       return "1";
     if (code == ServiceType._2)
       return "2";
@@ -2427,7 +2429,7 @@ public String toCode(ServiceType code) {
     if (code == ServiceType._629)
       return "629";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceUsclsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceUsclsEnumFactory.java
index 280515cf8f..832c6f697b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceUsclsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ServiceUsclsEnumFactory.java
@@ -80,7 +80,9 @@ public ServiceUscls fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(ServiceUscls code) {
-    if (code == ServiceUscls._1101)
+       if (code == ServiceUscls.NULL)
+           return null;
+       if (code == ServiceUscls._1101)
       return "1101";
     if (code == ServiceUscls._1102)
       return "1102";
@@ -119,7 +121,7 @@ public String toCode(ServiceUscls code) {
     if (code == ServiceUscls._99555)
       return "99555";
     return "?";
-  }
+   }
 
   public String toSystem(ServiceUscls code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SignatureTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SignatureTypeEnumFactory.java
index 9ff45b56a3..525bea3844 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SignatureTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SignatureTypeEnumFactory.java
@@ -78,7 +78,9 @@ public SignatureType fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(SignatureType code) {
-    if (code == SignatureType.OID_1_2_840_10065_1_12_1_1)
+       if (code == SignatureType.NULL)
+           return null;
+       if (code == SignatureType.OID_1_2_840_10065_1_12_1_1)
       return "1.2.840.10065.1.12.1.1";
     if (code == SignatureType.OID_1_2_840_10065_1_12_1_2)
       return "1.2.840.10065.1.12.1.2";
@@ -115,7 +117,7 @@ public String toCode(SignatureType code) {
     if (code == SignatureType.OID_1_2_840_10065_1_12_1_18)
       return "1.2.840.10065.1.12.1.18";
     return "?";
-  }
+   }
 
   public String toSystem(SignatureType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SlotstatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SlotstatusEnumFactory.java
index 6ffac1f241..b0c154a49c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SlotstatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SlotstatusEnumFactory.java
@@ -50,7 +50,9 @@ public Slotstatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Slotstatus code) {
-    if (code == Slotstatus.BUSY)
+       if (code == Slotstatus.NULL)
+           return null;
+       if (code == Slotstatus.BUSY)
       return "busy";
     if (code == Slotstatus.FREE)
       return "free";
@@ -59,7 +61,7 @@ public String toCode(Slotstatus code) {
     if (code == Slotstatus.BUSYTENTATIVE)
       return "busy-tentative";
     return "?";
-  }
+   }
 
   public String toSystem(Slotstatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecialValuesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecialValuesEnumFactory.java
index e4eb32c417..b44acde4b9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecialValuesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecialValuesEnumFactory.java
@@ -54,7 +54,9 @@ public SpecialValues fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(SpecialValues code) {
-    if (code == SpecialValues.TRUE)
+       if (code == SpecialValues.NULL)
+           return null;
+       if (code == SpecialValues.TRUE)
       return "true";
     if (code == SpecialValues.FALSE)
       return "false";
@@ -67,7 +69,7 @@ public String toCode(SpecialValues code) {
     if (code == SpecialValues.NILKNOWN)
       return "nil-known";
     return "?";
-  }
+   }
 
   public String toSystem(SpecialValues code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecimenStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecimenStatusEnumFactory.java
index 2a10eb0f0c..fe405200a5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecimenStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SpecimenStatusEnumFactory.java
@@ -50,7 +50,9 @@ public SpecimenStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(SpecimenStatus code) {
-    if (code == SpecimenStatus.AVAILABLE)
+       if (code == SpecimenStatus.NULL)
+           return null;
+       if (code == SpecimenStatus.AVAILABLE)
       return "available";
     if (code == SpecimenStatus.UNAVAILABLE)
       return "unavailable";
@@ -59,7 +61,7 @@ public String toCode(SpecimenStatus code) {
     if (code == SpecimenStatus.ENTEREDINERROR)
       return "entered-in-error";
     return "?";
-  }
+   }
 
   public String toSystem(SpecimenStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/StructureDefinitionKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/StructureDefinitionKindEnumFactory.java
index dc297d77d9..496f60f43e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/StructureDefinitionKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/StructureDefinitionKindEnumFactory.java
@@ -48,14 +48,16 @@ public StructureDefinitionKind fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(StructureDefinitionKind code) {
-    if (code == StructureDefinitionKind.DATATYPE)
+       if (code == StructureDefinitionKind.NULL)
+           return null;
+       if (code == StructureDefinitionKind.DATATYPE)
       return "datatype";
     if (code == StructureDefinitionKind.RESOURCE)
       return "resource";
     if (code == StructureDefinitionKind.LOGICAL)
       return "logical";
     return "?";
-  }
+   }
 
   public String toSystem(StructureDefinitionKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionChannelTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionChannelTypeEnumFactory.java
index 00a0f5a742..af5c10a061 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionChannelTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionChannelTypeEnumFactory.java
@@ -52,7 +52,9 @@ public SubscriptionChannelType fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(SubscriptionChannelType code) {
-    if (code == SubscriptionChannelType.RESTHOOK)
+       if (code == SubscriptionChannelType.NULL)
+           return null;
+       if (code == SubscriptionChannelType.RESTHOOK)
       return "rest-hook";
     if (code == SubscriptionChannelType.WEBSOCKET)
       return "websocket";
@@ -63,7 +65,7 @@ public String toCode(SubscriptionChannelType code) {
     if (code == SubscriptionChannelType.MESSAGE)
       return "message";
     return "?";
-  }
+   }
 
   public String toSystem(SubscriptionChannelType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionStatusEnumFactory.java
index 5bb235f89a..6f6f5b8d97 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionStatusEnumFactory.java
@@ -50,7 +50,9 @@ public SubscriptionStatus fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(SubscriptionStatus code) {
-    if (code == SubscriptionStatus.REQUESTED)
+       if (code == SubscriptionStatus.NULL)
+           return null;
+       if (code == SubscriptionStatus.REQUESTED)
       return "requested";
     if (code == SubscriptionStatus.ACTIVE)
       return "active";
@@ -59,7 +61,7 @@ public String toCode(SubscriptionStatus code) {
     if (code == SubscriptionStatus.OFF)
       return "off";
     return "?";
-  }
+   }
 
   public String toSystem(SubscriptionStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionTagEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionTagEnumFactory.java
index 1936a8dcb6..5861cc8d45 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionTagEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubscriptionTagEnumFactory.java
@@ -46,12 +46,14 @@ public SubscriptionTag fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(SubscriptionTag code) {
-    if (code == SubscriptionTag.QUEUED)
+       if (code == SubscriptionTag.NULL)
+           return null;
+       if (code == SubscriptionTag.QUEUED)
       return "queued";
     if (code == SubscriptionTag.DELIVERED)
       return "delivered";
     return "?";
-  }
+   }
 
   public String toSystem(SubscriptionTag code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubstanceCategoryEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubstanceCategoryEnumFactory.java
index d56c711926..7f8f9a22dc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubstanceCategoryEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SubstanceCategoryEnumFactory.java
@@ -56,7 +56,9 @@ public SubstanceCategory fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(SubstanceCategory code) {
-    if (code == SubstanceCategory.ALLERGEN)
+       if (code == SubstanceCategory.NULL)
+           return null;
+       if (code == SubstanceCategory.ALLERGEN)
       return "allergen";
     if (code == SubstanceCategory.BIOLOGICAL)
       return "biological";
@@ -71,7 +73,7 @@ public String toCode(SubstanceCategory code) {
     if (code == SubstanceCategory.MATERIAL)
       return "material";
     return "?";
-  }
+   }
 
   public String toSystem(SubstanceCategory code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryStatusEnumFactory.java
index 77aaec53ee..8a0f08b939 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryStatusEnumFactory.java
@@ -48,14 +48,16 @@ public SupplydeliveryStatus fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(SupplydeliveryStatus code) {
-    if (code == SupplydeliveryStatus.INPROGRESS)
+       if (code == SupplydeliveryStatus.NULL)
+           return null;
+       if (code == SupplydeliveryStatus.INPROGRESS)
       return "in-progress";
     if (code == SupplydeliveryStatus.COMPLETED)
       return "completed";
     if (code == SupplydeliveryStatus.ABANDONED)
       return "abandoned";
     return "?";
-  }
+   }
 
   public String toSystem(SupplydeliveryStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryTypeEnumFactory.java
index 9a74cbaa5b..ca44de07bc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplydeliveryTypeEnumFactory.java
@@ -46,12 +46,14 @@ public SupplydeliveryType fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(SupplydeliveryType code) {
-    if (code == SupplydeliveryType.MEDICATION)
+       if (code == SupplydeliveryType.NULL)
+           return null;
+       if (code == SupplydeliveryType.MEDICATION)
       return "medication";
     if (code == SupplydeliveryType.DEVICE)
       return "device";
     return "?";
-  }
+   }
 
   public String toSystem(SupplydeliveryType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestKindEnumFactory.java
index 76c2619203..296feea6de 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestKindEnumFactory.java
@@ -46,12 +46,14 @@ public SupplyrequestKind fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(SupplyrequestKind code) {
-    if (code == SupplyrequestKind.CENTRAL)
+       if (code == SupplyrequestKind.NULL)
+           return null;
+       if (code == SupplyrequestKind.CENTRAL)
       return "central";
     if (code == SupplyrequestKind.NONSTOCK)
       return "nonstock";
     return "?";
-  }
+   }
 
   public String toSystem(SupplyrequestKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestReasonEnumFactory.java
index 40d19a46aa..1bfd443961 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestReasonEnumFactory.java
@@ -46,12 +46,14 @@ public SupplyrequestReason fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(SupplyrequestReason code) {
-    if (code == SupplyrequestReason.PATIENTCARE)
+       if (code == SupplyrequestReason.NULL)
+           return null;
+       if (code == SupplyrequestReason.PATIENTCARE)
       return "patient-care";
     if (code == SupplyrequestReason.WARDSTOCK)
       return "ward-stock";
     return "?";
-  }
+   }
 
   public String toSystem(SupplyrequestReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestStatusEnumFactory.java
index c8b3d1570a..31dff25251 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SupplyrequestStatusEnumFactory.java
@@ -50,7 +50,9 @@ public SupplyrequestStatus fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(SupplyrequestStatus code) {
-    if (code == SupplyrequestStatus.REQUESTED)
+       if (code == SupplyrequestStatus.NULL)
+           return null;
+       if (code == SupplyrequestStatus.REQUESTED)
       return "requested";
     if (code == SupplyrequestStatus.COMPLETED)
       return "completed";
@@ -59,7 +61,7 @@ public String toCode(SupplyrequestStatus code) {
     if (code == SupplyrequestStatus.CANCELLED)
       return "cancelled";
     return "?";
-  }
+   }
 
   public String toSystem(SupplyrequestStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SurfaceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SurfaceEnumFactory.java
index 33e630c3fe..7df94d1c5c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SurfaceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/SurfaceEnumFactory.java
@@ -64,7 +64,9 @@ public Surface fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Surface code) {
-    if (code == Surface.M)
+       if (code == Surface.NULL)
+           return null;
+       if (code == Surface.M)
       return "M";
     if (code == Surface.O)
       return "O";
@@ -87,7 +89,7 @@ public String toCode(Surface code) {
     if (code == Surface.MOD)
       return "MOD";
     return "?";
-  }
+   }
 
   public String toSystem(Surface code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPerformerTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPerformerTypeEnumFactory.java
index dc1e279999..49cb622cb8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPerformerTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPerformerTypeEnumFactory.java
@@ -58,7 +58,9 @@ public TaskPerformerType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(TaskPerformerType code) {
-    if (code == TaskPerformerType.REQUESTER)
+       if (code == TaskPerformerType.NULL)
+           return null;
+       if (code == TaskPerformerType.REQUESTER)
       return "requester";
     if (code == TaskPerformerType.DISPATCHER)
       return "dispatcher";
@@ -75,7 +77,7 @@ public String toCode(TaskPerformerType code) {
     if (code == TaskPerformerType.REVIEWER)
       return "reviewer";
     return "?";
-  }
+   }
 
   public String toSystem(TaskPerformerType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPriorityEnumFactory.java
index 810ac84668..de4d32845b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskPriorityEnumFactory.java
@@ -48,14 +48,16 @@ public TaskPriority fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(TaskPriority code) {
-    if (code == TaskPriority.LOW)
+       if (code == TaskPriority.NULL)
+           return null;
+       if (code == TaskPriority.LOW)
       return "low";
     if (code == TaskPriority.NORMAL)
       return "normal";
     if (code == TaskPriority.HIGH)
       return "high";
     return "?";
-  }
+   }
 
   public String toSystem(TaskPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskStatusEnumFactory.java
index f6cbf07831..c588e78749 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TaskStatusEnumFactory.java
@@ -62,7 +62,9 @@ public TaskStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(TaskStatus code) {
-    if (code == TaskStatus.DRAFT)
+       if (code == TaskStatus.NULL)
+           return null;
+       if (code == TaskStatus.DRAFT)
       return "draft";
     if (code == TaskStatus.REQUESTED)
       return "requested";
@@ -83,7 +85,7 @@ public String toCode(TaskStatus code) {
     if (code == TaskStatus.COMPLETED)
       return "completed";
     return "?";
-  }
+   }
 
   public String toSystem(TaskStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TeethEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TeethEnumFactory.java
index e40022e43e..00f01af96f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TeethEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TeethEnumFactory.java
@@ -106,7 +106,9 @@ public Teeth fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Teeth code) {
-    if (code == Teeth._11)
+       if (code == Teeth.NULL)
+           return null;
+       if (code == Teeth._11)
       return "11";
     if (code == Teeth._12)
       return "12";
@@ -171,7 +173,7 @@ public String toCode(Teeth code) {
     if (code == Teeth._48)
       return "48";
     return "?";
-  }
+   }
 
   public String toSystem(Teeth code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptOperationCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptOperationCodesEnumFactory.java
index 314118c444..7e37075038 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptOperationCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptOperationCodesEnumFactory.java
@@ -124,7 +124,9 @@ public TestscriptOperationCodes fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(TestscriptOperationCodes code) {
-    if (code == TestscriptOperationCodes.READ)
+       if (code == TestscriptOperationCodes.NULL)
+           return null;
+       if (code == TestscriptOperationCodes.READ)
       return "read";
     if (code == TestscriptOperationCodes.VREAD)
       return "vread";
@@ -207,7 +209,7 @@ public String toCode(TestscriptOperationCodes code) {
     if (code == TestscriptOperationCodes.VALIDATECODE)
       return "validate-code";
     return "?";
-  }
+   }
 
   public String toSystem(TestscriptOperationCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileDestinationTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileDestinationTypesEnumFactory.java
index 29cb282c97..229e851d5b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileDestinationTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileDestinationTypesEnumFactory.java
@@ -50,7 +50,9 @@ public TestscriptProfileDestinationTypes fromCode(String codeString) throws Ille
   }
 
   public String toCode(TestscriptProfileDestinationTypes code) {
-    if (code == TestscriptProfileDestinationTypes.FHIRSERVER)
+       if (code == TestscriptProfileDestinationTypes.NULL)
+           return null;
+       if (code == TestscriptProfileDestinationTypes.FHIRSERVER)
       return "FHIR-Server";
     if (code == TestscriptProfileDestinationTypes.FHIRSDCFORMMANAGER)
       return "FHIR-SDC-FormManager";
@@ -59,7 +61,7 @@ public String toCode(TestscriptProfileDestinationTypes code) {
     if (code == TestscriptProfileDestinationTypes.FHIRSDCFORMRECEIVER)
       return "FHIR-SDC-FormReceiver";
     return "?";
-  }
+   }
 
   public String toSystem(TestscriptProfileDestinationTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileOriginTypesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileOriginTypesEnumFactory.java
index 766d5c179c..b490a244f6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileOriginTypesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TestscriptProfileOriginTypesEnumFactory.java
@@ -46,12 +46,14 @@ public TestscriptProfileOriginTypes fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(TestscriptProfileOriginTypes code) {
-    if (code == TestscriptProfileOriginTypes.FHIRCLIENT)
+       if (code == TestscriptProfileOriginTypes.NULL)
+           return null;
+       if (code == TestscriptProfileOriginTypes.FHIRCLIENT)
       return "FHIR-Client";
     if (code == TestscriptProfileOriginTypes.FHIRSDCFORMFILLER)
       return "FHIR-SDC-FormFiller";
     return "?";
-  }
+   }
 
   public String toSystem(TestscriptProfileOriginTypes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TimingAbbreviationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TimingAbbreviationEnumFactory.java
index 35849a7444..49c1a2788e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TimingAbbreviationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TimingAbbreviationEnumFactory.java
@@ -50,7 +50,9 @@ public TimingAbbreviation fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(TimingAbbreviation code) {
-    if (code == TimingAbbreviation.QD)
+       if (code == TimingAbbreviation.NULL)
+           return null;
+       if (code == TimingAbbreviation.QD)
       return "QD";
     if (code == TimingAbbreviation.QOD)
       return "QOD";
@@ -59,7 +61,7 @@ public String toCode(TimingAbbreviation code) {
     if (code == TimingAbbreviation.Q6H)
       return "Q6H";
     return "?";
-  }
+   }
 
   public String toSystem(TimingAbbreviation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ToothEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ToothEnumFactory.java
index 59b6f7d99d..3629ca5283 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ToothEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ToothEnumFactory.java
@@ -124,7 +124,9 @@ public Tooth fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Tooth code) {
-    if (code == Tooth._0)
+       if (code == Tooth.NULL)
+           return null;
+       if (code == Tooth._0)
       return "0";
     if (code == Tooth._1)
       return "1";
@@ -207,7 +209,7 @@ public String toCode(Tooth code) {
     if (code == Tooth._48)
       return "48";
     return "?";
-  }
+   }
 
   public String toSystem(Tooth code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TransactionModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TransactionModeEnumFactory.java
index 217f53f83f..662390d5ab 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TransactionModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TransactionModeEnumFactory.java
@@ -50,7 +50,9 @@ public TransactionMode fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(TransactionMode code) {
-    if (code == TransactionMode.NOTSUPPORTED)
+       if (code == TransactionMode.NULL)
+           return null;
+       if (code == TransactionMode.NOTSUPPORTED)
       return "not-supported";
     if (code == TransactionMode.BATCH)
       return "batch";
@@ -59,7 +61,7 @@ public String toCode(TransactionMode code) {
     if (code == TransactionMode.BOTH)
       return "both";
     return "?";
-  }
+   }
 
   public String toSystem(TransactionMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TriggerTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TriggerTypeEnumFactory.java
index 641d32dcb5..2a4b043272 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TriggerTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TriggerTypeEnumFactory.java
@@ -56,7 +56,9 @@ public TriggerType fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(TriggerType code) {
-    if (code == TriggerType.NAMEDEVENT)
+       if (code == TriggerType.NULL)
+           return null;
+       if (code == TriggerType.NAMEDEVENT)
       return "named-event";
     if (code == TriggerType.PERIODIC)
       return "periodic";
@@ -71,7 +73,7 @@ public String toCode(TriggerType code) {
     if (code == TriggerType.DATAACCESSENDED)
       return "data-access-ended";
     return "?";
-  }
+   }
 
   public String toSystem(TriggerType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TypeDerivationRuleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TypeDerivationRuleEnumFactory.java
index 05a89a3f3d..c33a1e4831 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TypeDerivationRuleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/TypeDerivationRuleEnumFactory.java
@@ -46,12 +46,14 @@ public TypeDerivationRule fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(TypeDerivationRule code) {
-    if (code == TypeDerivationRule.SPECIALIZATION)
+       if (code == TypeDerivationRule.NULL)
+           return null;
+       if (code == TypeDerivationRule.SPECIALIZATION)
       return "specialization";
     if (code == TypeDerivationRule.CONSTRAINT)
       return "constraint";
     return "?";
-  }
+   }
 
   public String toSystem(TypeDerivationRule code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UdiEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UdiEnumFactory.java
index d984852a1f..a52f06a43a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UdiEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UdiEnumFactory.java
@@ -44,10 +44,12 @@ public Udi fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(Udi code) {
-    if (code == Udi.GUDID)
+       if (code == Udi.NULL)
+           return null;
+       if (code == Udi.GUDID)
       return "gudid";
     return "?";
-  }
+   }
 
   public String toSystem(Udi code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UnknownContentCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UnknownContentCodeEnumFactory.java
index 16b69c5831..53d050b4e5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UnknownContentCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UnknownContentCodeEnumFactory.java
@@ -50,7 +50,9 @@ public UnknownContentCode fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(UnknownContentCode code) {
-    if (code == UnknownContentCode.NO)
+       if (code == UnknownContentCode.NULL)
+           return null;
+       if (code == UnknownContentCode.NO)
       return "no";
     if (code == UnknownContentCode.EXTENSIONS)
       return "extensions";
@@ -59,7 +61,7 @@ public String toCode(UnknownContentCode code) {
     if (code == UnknownContentCode.BOTH)
       return "both";
     return "?";
-  }
+   }
 
   public String toSystem(UnknownContentCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabDoEventEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabDoEventEnumFactory.java
index 0d37e9efa0..46b816bf28 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabDoEventEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabDoEventEnumFactory.java
@@ -50,7 +50,9 @@ public UslabDoEvent fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(UslabDoEvent code) {
-    if (code == UslabDoEvent.NEWREQUEST)
+       if (code == UslabDoEvent.NULL)
+           return null;
+       if (code == UslabDoEvent.NEWREQUEST)
       return "new-request";
     if (code == UslabDoEvent.ADDONREQUEST)
       return "add-on-request";
@@ -59,7 +61,7 @@ public String toCode(UslabDoEvent code) {
     if (code == UslabDoEvent.LABCANCEL)
       return "lab-cancel";
     return "?";
-  }
+   }
 
   public String toSystem(UslabDoEvent code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabObsKindEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabObsKindEnumFactory.java
index 986d1e27df..e1f47efe6d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabObsKindEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/UslabObsKindEnumFactory.java
@@ -48,14 +48,16 @@ public UslabObsKind fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(UslabObsKind code) {
-    if (code == UslabObsKind.RESULT)
+       if (code == UslabObsKind.NULL)
+           return null;
+       if (code == UslabObsKind.RESULT)
       return "result";
     if (code == UslabObsKind.RESPONSE)
       return "response";
     if (code == UslabObsKind.INFORMATION)
       return "information";
     return "?";
-  }
+   }
 
   public String toSystem(UslabObsKind code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementConditionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementConditionEnumFactory.java
index 7c109856be..3d41d00591 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementConditionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementConditionEnumFactory.java
@@ -50,7 +50,9 @@ public V3AcknowledgementCondition fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(V3AcknowledgementCondition code) {
-    if (code == V3AcknowledgementCondition.AL)
+       if (code == V3AcknowledgementCondition.NULL)
+           return null;
+       if (code == V3AcknowledgementCondition.AL)
       return "AL";
     if (code == V3AcknowledgementCondition.ER)
       return "ER";
@@ -59,7 +61,7 @@ public String toCode(V3AcknowledgementCondition code) {
     if (code == V3AcknowledgementCondition.SU)
       return "SU";
     return "?";
-  }
+   }
 
   public String toSystem(V3AcknowledgementCondition code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailCodeEnumFactory.java
index 05c52b90bd..dd9695d810 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailCodeEnumFactory.java
@@ -98,7 +98,9 @@ public V3AcknowledgementDetailCode fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3AcknowledgementDetailCode code) {
-    if (code == V3AcknowledgementDetailCode._ACKNOWLEDGEMENTDETAILNOTSUPPORTEDCODE)
+       if (code == V3AcknowledgementDetailCode.NULL)
+           return null;
+       if (code == V3AcknowledgementDetailCode._ACKNOWLEDGEMENTDETAILNOTSUPPORTEDCODE)
       return "_AcknowledgementDetailNotSupportedCode";
     if (code == V3AcknowledgementDetailCode.NS200)
       return "NS200";
@@ -155,7 +157,7 @@ public String toCode(V3AcknowledgementDetailCode code) {
     if (code == V3AcknowledgementDetailCode.SYN113)
       return "SYN113";
     return "?";
-  }
+   }
 
   public String toSystem(V3AcknowledgementDetailCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailTypeEnumFactory.java
index 6c5a1edff3..87256fe55d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementDetailTypeEnumFactory.java
@@ -54,7 +54,9 @@ public V3AcknowledgementDetailType fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3AcknowledgementDetailType code) {
-    if (code == V3AcknowledgementDetailType.E)
+       if (code == V3AcknowledgementDetailType.NULL)
+           return null;
+       if (code == V3AcknowledgementDetailType.E)
       return "E";
     if (code == V3AcknowledgementDetailType.I)
       return "I";
@@ -67,7 +69,7 @@ public String toCode(V3AcknowledgementDetailType code) {
     if (code == V3AcknowledgementDetailType.WARN)
       return "WARN";
     return "?";
-  }
+   }
 
   public String toSystem(V3AcknowledgementDetailType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementTypeEnumFactory.java
index c352f1a348..832ec72d05 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AcknowledgementTypeEnumFactory.java
@@ -54,7 +54,9 @@ public V3AcknowledgementType fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3AcknowledgementType code) {
-    if (code == V3AcknowledgementType.AA)
+       if (code == V3AcknowledgementType.NULL)
+           return null;
+       if (code == V3AcknowledgementType.AA)
       return "AA";
     if (code == V3AcknowledgementType.AE)
       return "AE";
@@ -67,7 +69,7 @@ public String toCode(V3AcknowledgementType code) {
     if (code == V3AcknowledgementType.CR)
       return "CR";
     return "?";
-  }
+   }
 
   public String toSystem(V3AcknowledgementType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActClassEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActClassEnumFactory.java
index 10daa28a7e..45a2934b39 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActClassEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActClassEnumFactory.java
@@ -290,7 +290,9 @@ public V3ActClass fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActClass code) {
-    if (code == V3ActClass.ACT)
+       if (code == V3ActClass.NULL)
+           return null;
+       if (code == V3ActClass.ACT)
       return "ACT";
     if (code == V3ActClass._ACTCLASSRECORDORGANIZER)
       return "_ActClassRecordOrganizer";
@@ -539,7 +541,7 @@ public String toCode(V3ActClass code) {
     if (code == V3ActClass.UNORDERED)
       return "unordered";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActClass code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActCodeEnumFactory.java
index dd782023f7..16a3b49e68 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActCodeEnumFactory.java
@@ -2224,7 +2224,9 @@ public V3ActCode fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActCode code) {
-    if (code == V3ActCode._ACTACCOUNTCODE)
+       if (code == V3ActCode.NULL)
+           return null;
+       if (code == V3ActCode._ACTACCOUNTCODE)
       return "_ActAccountCode";
     if (code == V3ActCode.ACCTRECEIVABLE)
       return "ACCTRECEIVABLE";
@@ -4407,7 +4409,7 @@ public String toCode(V3ActCode code) {
     if (code == V3ActCode.STORE)
       return "STORE";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActExposureLevelCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActExposureLevelCodeEnumFactory.java
index 4a4eec6d80..d3d23073cc 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActExposureLevelCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActExposureLevelCodeEnumFactory.java
@@ -50,7 +50,9 @@ public V3ActExposureLevelCode fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3ActExposureLevelCode code) {
-    if (code == V3ActExposureLevelCode._ACTEXPOSURELEVELCODE)
+       if (code == V3ActExposureLevelCode.NULL)
+           return null;
+       if (code == V3ActExposureLevelCode._ACTEXPOSURELEVELCODE)
       return "_ActExposureLevelCode";
     if (code == V3ActExposureLevelCode.HIGH)
       return "HIGH";
@@ -59,7 +61,7 @@ public String toCode(V3ActExposureLevelCode code) {
     if (code == V3ActExposureLevelCode.MEDIUM)
       return "MEDIUM";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActExposureLevelCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActInvoiceElementModifierEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActInvoiceElementModifierEnumFactory.java
index 555803ac1e..cdc737f034 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActInvoiceElementModifierEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActInvoiceElementModifierEnumFactory.java
@@ -50,7 +50,9 @@ public V3ActInvoiceElementModifier fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3ActInvoiceElementModifier code) {
-    if (code == V3ActInvoiceElementModifier.EFORM)
+       if (code == V3ActInvoiceElementModifier.NULL)
+           return null;
+       if (code == V3ActInvoiceElementModifier.EFORM)
       return "EFORM";
     if (code == V3ActInvoiceElementModifier.FAX)
       return "FAX";
@@ -59,7 +61,7 @@ public String toCode(V3ActInvoiceElementModifier code) {
     if (code == V3ActInvoiceElementModifier.PAPER)
       return "PAPER";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActInvoiceElementModifier code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActMoodEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActMoodEnumFactory.java
index 03cc09d2b4..0ce9aa4152 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActMoodEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActMoodEnumFactory.java
@@ -98,7 +98,9 @@ public V3ActMood fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActMood code) {
-    if (code == V3ActMood._ACTMOODCOMPLETIONTRACK)
+       if (code == V3ActMood.NULL)
+           return null;
+       if (code == V3ActMood._ACTMOODCOMPLETIONTRACK)
       return "_ActMoodCompletionTrack";
     if (code == V3ActMood._ACTMOODPOTENTIAL)
       return "_ActMoodPotential";
@@ -155,7 +157,7 @@ public String toCode(V3ActMood code) {
     if (code == V3ActMood.OPT)
       return "OPT";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActMood code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActPriorityEnumFactory.java
index 4ebbf4ecff..da3edad10c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActPriorityEnumFactory.java
@@ -72,7 +72,9 @@ public V3ActPriority fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3ActPriority code) {
-    if (code == V3ActPriority.A)
+       if (code == V3ActPriority.NULL)
+           return null;
+       if (code == V3ActPriority.A)
       return "A";
     if (code == V3ActPriority.CR)
       return "CR";
@@ -103,7 +105,7 @@ public String toCode(V3ActPriority code) {
     if (code == V3ActPriority.UR)
       return "UR";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActReasonEnumFactory.java
index 57392e7040..27f1f15ff5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActReasonEnumFactory.java
@@ -566,7 +566,9 @@ public V3ActReason fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActReason code) {
-    if (code == V3ActReason._ACTACCOMMODATIONREASON)
+       if (code == V3ActReason.NULL)
+           return null;
+       if (code == V3ActReason._ACTACCOMMODATIONREASON)
       return "_ActAccommodationReason";
     if (code == V3ActReason.ACCREQNA)
       return "ACCREQNA";
@@ -1091,7 +1093,7 @@ public String toCode(V3ActReason code) {
     if (code == V3ActReason.TRAN)
       return "TRAN";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipCheckpointEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipCheckpointEnumFactory.java
index 67e0a0b7d0..5b818cf97f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipCheckpointEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipCheckpointEnumFactory.java
@@ -52,7 +52,9 @@ public V3ActRelationshipCheckpoint fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3ActRelationshipCheckpoint code) {
-    if (code == V3ActRelationshipCheckpoint.B)
+       if (code == V3ActRelationshipCheckpoint.NULL)
+           return null;
+       if (code == V3ActRelationshipCheckpoint.B)
       return "B";
     if (code == V3ActRelationshipCheckpoint.E)
       return "E";
@@ -63,7 +65,7 @@ public String toCode(V3ActRelationshipCheckpoint code) {
     if (code == V3ActRelationshipCheckpoint.X)
       return "X";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActRelationshipCheckpoint code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipJoinEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipJoinEnumFactory.java
index d8849ad430..71e4b082a4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipJoinEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipJoinEnumFactory.java
@@ -50,7 +50,9 @@ public V3ActRelationshipJoin fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3ActRelationshipJoin code) {
-    if (code == V3ActRelationshipJoin.D)
+       if (code == V3ActRelationshipJoin.NULL)
+           return null;
+       if (code == V3ActRelationshipJoin.D)
       return "D";
     if (code == V3ActRelationshipJoin.K)
       return "K";
@@ -59,7 +61,7 @@ public String toCode(V3ActRelationshipJoin code) {
     if (code == V3ActRelationshipJoin.X)
       return "X";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActRelationshipJoin code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSplitEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSplitEnumFactory.java
index 2f0cb32038..fc6487d50d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSplitEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSplitEnumFactory.java
@@ -50,7 +50,9 @@ public V3ActRelationshipSplit fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3ActRelationshipSplit code) {
-    if (code == V3ActRelationshipSplit.E1)
+       if (code == V3ActRelationshipSplit.NULL)
+           return null;
+       if (code == V3ActRelationshipSplit.E1)
       return "E1";
     if (code == V3ActRelationshipSplit.EW)
       return "EW";
@@ -59,7 +61,7 @@ public String toCode(V3ActRelationshipSplit code) {
     if (code == V3ActRelationshipSplit.IW)
       return "IW";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActRelationshipSplit code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSubsetEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSubsetEnumFactory.java
index 1959546322..6d0a718f30 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSubsetEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipSubsetEnumFactory.java
@@ -70,7 +70,9 @@ public V3ActRelationshipSubset fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3ActRelationshipSubset code) {
-    if (code == V3ActRelationshipSubset._PARTICIPATIONSUBSET)
+       if (code == V3ActRelationshipSubset.NULL)
+           return null;
+       if (code == V3ActRelationshipSubset._PARTICIPATIONSUBSET)
       return "_ParticipationSubset";
     if (code == V3ActRelationshipSubset.FUTURE)
       return "FUTURE";
@@ -99,7 +101,7 @@ public String toCode(V3ActRelationshipSubset code) {
     if (code == V3ActRelationshipSubset.MIN)
       return "MIN";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActRelationshipSubset code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipTypeEnumFactory.java
index c96b59ceb9..9efd71581f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActRelationshipTypeEnumFactory.java
@@ -316,7 +316,9 @@ public V3ActRelationshipType fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3ActRelationshipType code) {
-    if (code == V3ActRelationshipType.ART)
+       if (code == V3ActRelationshipType.NULL)
+           return null;
+       if (code == V3ActRelationshipType.ART)
       return "ART";
     if (code == V3ActRelationshipType._ACTCLASSTEMPORALLYPERTAINS)
       return "_ActClassTemporallyPertains";
@@ -591,7 +593,7 @@ public String toCode(V3ActRelationshipType code) {
     if (code == V3ActRelationshipType.SUGG)
       return "SUGG";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActRelationshipType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActSiteEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActSiteEnumFactory.java
index 40a63f21d3..7ec192fa3c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActSiteEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActSiteEnumFactory.java
@@ -150,7 +150,9 @@ public V3ActSite fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActSite code) {
-    if (code == V3ActSite._HUMANACTSITE)
+       if (code == V3ActSite.NULL)
+           return null;
+       if (code == V3ActSite._HUMANACTSITE)
       return "_HumanActSite";
     if (code == V3ActSite._HUMANSUBSTANCEADMINISTRATIONSITE)
       return "_HumanSubstanceAdministrationSite";
@@ -259,7 +261,7 @@ public String toCode(V3ActSite code) {
     if (code == V3ActSite.RVL)
       return "RVL";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActSite code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActStatusEnumFactory.java
index 8452ffc380..342790d4e8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActStatusEnumFactory.java
@@ -62,7 +62,9 @@ public V3ActStatus fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3ActStatus code) {
-    if (code == V3ActStatus.NORMAL)
+       if (code == V3ActStatus.NULL)
+           return null;
+       if (code == V3ActStatus.NORMAL)
       return "normal";
     if (code == V3ActStatus.ABORTED)
       return "aborted";
@@ -83,7 +85,7 @@ public String toCode(V3ActStatus code) {
     if (code == V3ActStatus.OBSOLETE)
       return "obsolete";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUSPrivacyLawEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUSPrivacyLawEnumFactory.java
index 626ee1296b..d5702b360d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUSPrivacyLawEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUSPrivacyLawEnumFactory.java
@@ -56,7 +56,9 @@ public V3ActUSPrivacyLaw fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3ActUSPrivacyLaw code) {
-    if (code == V3ActUSPrivacyLaw._ACTUSPRIVACYLAW)
+       if (code == V3ActUSPrivacyLaw.NULL)
+           return null;
+       if (code == V3ActUSPrivacyLaw._ACTUSPRIVACYLAW)
       return "_ActUSPrivacyLaw";
     if (code == V3ActUSPrivacyLaw._42CFRPART2)
       return "42CFRPart2";
@@ -71,7 +73,7 @@ public String toCode(V3ActUSPrivacyLaw code) {
     if (code == V3ActUSPrivacyLaw.TITLE38SECTION7332)
       return "Title38Section7332";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActUSPrivacyLaw code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUncertaintyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUncertaintyEnumFactory.java
index 52c4264f8c..ae9d4a7253 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUncertaintyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ActUncertaintyEnumFactory.java
@@ -46,12 +46,14 @@ public V3ActUncertainty fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3ActUncertainty code) {
-    if (code == V3ActUncertainty.N)
+       if (code == V3ActUncertainty.NULL)
+           return null;
+       if (code == V3ActUncertainty.N)
       return "N";
     if (code == V3ActUncertainty.U)
       return "U";
     return "?";
-  }
+   }
 
   public String toSystem(V3ActUncertainty code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressPartTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressPartTypeEnumFactory.java
index 708eae89da..ac04e18652 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressPartTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressPartTypeEnumFactory.java
@@ -102,7 +102,9 @@ public V3AddressPartType fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3AddressPartType code) {
-    if (code == V3AddressPartType.ADL)
+       if (code == V3AddressPartType.NULL)
+           return null;
+       if (code == V3AddressPartType.ADL)
       return "ADL";
     if (code == V3AddressPartType.AL)
       return "AL";
@@ -163,7 +165,7 @@ public String toCode(V3AddressPartType code) {
     if (code == V3AddressPartType.ZIP)
       return "ZIP";
     return "?";
-  }
+   }
 
   public String toSystem(V3AddressPartType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressUseEnumFactory.java
index bb29725775..56417c6745 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AddressUseEnumFactory.java
@@ -80,7 +80,9 @@ public V3AddressUse fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3AddressUse code) {
-    if (code == V3AddressUse._GENERALADDRESSUSE)
+       if (code == V3AddressUse.NULL)
+           return null;
+       if (code == V3AddressUse._GENERALADDRESSUSE)
       return "_GeneralAddressUse";
     if (code == V3AddressUse.BAD)
       return "BAD";
@@ -119,7 +121,7 @@ public String toCode(V3AddressUse code) {
     if (code == V3AddressUse.PG)
       return "PG";
     return "?";
-  }
+   }
 
   public String toSystem(V3AddressUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AdministrativeGenderEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AdministrativeGenderEnumFactory.java
index 80ec23fe7c..86707d07a1 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AdministrativeGenderEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AdministrativeGenderEnumFactory.java
@@ -48,14 +48,16 @@ public V3AdministrativeGender fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3AdministrativeGender code) {
-    if (code == V3AdministrativeGender.F)
+       if (code == V3AdministrativeGender.NULL)
+           return null;
+       if (code == V3AdministrativeGender.F)
       return "F";
     if (code == V3AdministrativeGender.M)
       return "M";
     if (code == V3AdministrativeGender.UN)
       return "UN";
     return "?";
-  }
+   }
 
   public String toSystem(V3AdministrativeGender code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AmericanIndianAlaskaNativeLanguagesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AmericanIndianAlaskaNativeLanguagesEnumFactory.java
index 9f43bc7a2e..fa7f3fe0f5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AmericanIndianAlaskaNativeLanguagesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3AmericanIndianAlaskaNativeLanguagesEnumFactory.java
@@ -553,7 +553,9 @@ public V3AmericanIndianAlaskaNativeLanguages fromCode(String codeString) throws
   }
 
   public String toCode(V3AmericanIndianAlaskaNativeLanguages code) {
-    if (code == V3AmericanIndianAlaskaNativeLanguages._ALGIC)
+       if (code == V3AmericanIndianAlaskaNativeLanguages.NULL)
+           return null;
+       if (code == V3AmericanIndianAlaskaNativeLanguages._ALGIC)
       return "_Algic";
     if (code == V3AmericanIndianAlaskaNativeLanguages._ALGONQUIAN)
       return "_Algonquian";
@@ -1064,7 +1066,7 @@ public String toCode(V3AmericanIndianAlaskaNativeLanguages code) {
     if (code == V3AmericanIndianAlaskaNativeLanguages.XZUN)
       return "x-ZUN";
     return "?";
-  }
+   }
 
   public String toSystem(V3AmericanIndianAlaskaNativeLanguages code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarCycleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarCycleEnumFactory.java
index ce93e0c0c9..c7caf22455 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarCycleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarCycleEnumFactory.java
@@ -78,7 +78,9 @@ public V3CalendarCycle fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3CalendarCycle code) {
-    if (code == V3CalendarCycle._CALENDARCYCLEONELETTER)
+       if (code == V3CalendarCycle.NULL)
+           return null;
+       if (code == V3CalendarCycle._CALENDARCYCLEONELETTER)
       return "_CalendarCycleOneLetter";
     if (code == V3CalendarCycle.CW)
       return "CW";
@@ -115,7 +117,7 @@ public String toCode(V3CalendarCycle code) {
     if (code == V3CalendarCycle.WM)
       return "WM";
     return "?";
-  }
+   }
 
   public String toSystem(V3CalendarCycle code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarEnumFactory.java
index 1a9b248574..0e8e12f2c7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarEnumFactory.java
@@ -44,10 +44,12 @@ public V3Calendar fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3Calendar code) {
-    if (code == V3Calendar.GREG)
+       if (code == V3Calendar.NULL)
+           return null;
+       if (code == V3Calendar.GREG)
       return "GREG";
     return "?";
-  }
+   }
 
   public String toSystem(V3Calendar code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarTypeEnumFactory.java
index 78d3d27229..25995dd3f3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CalendarTypeEnumFactory.java
@@ -44,10 +44,12 @@ public V3CalendarType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3CalendarType code) {
-    if (code == V3CalendarType.GREG)
+       if (code == V3CalendarType.NULL)
+           return null;
+       if (code == V3CalendarType.GREG)
       return "GREG";
     return "?";
-  }
+   }
 
   public String toSystem(V3CalendarType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CharsetEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CharsetEnumFactory.java
index 63a5e72337..3a239c9e8d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CharsetEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CharsetEnumFactory.java
@@ -62,7 +62,9 @@ public V3Charset fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3Charset code) {
-    if (code == V3Charset.EBCDIC)
+       if (code == V3Charset.NULL)
+           return null;
+       if (code == V3Charset.EBCDIC)
       return "EBCDIC";
     if (code == V3Charset.ISO10646UCS2)
       return "ISO-10646-UCS-2";
@@ -83,7 +85,7 @@ public String toCode(V3Charset code) {
     if (code == V3Charset.UTF8)
       return "UTF-8";
     return "?";
-  }
+   }
 
   public String toSystem(V3Charset code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CodingRationaleEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CodingRationaleEnumFactory.java
index 6599100f40..9e606c674c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CodingRationaleEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CodingRationaleEnumFactory.java
@@ -58,7 +58,9 @@ public V3CodingRationale fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3CodingRationale code) {
-    if (code == V3CodingRationale.O)
+       if (code == V3CodingRationale.NULL)
+           return null;
+       if (code == V3CodingRationale.O)
       return "O";
     if (code == V3CodingRationale.OR)
       return "OR";
@@ -75,7 +77,7 @@ public String toCode(V3CodingRationale code) {
     if (code == V3CodingRationale.SRC)
       return "SRC";
     return "?";
-  }
+   }
 
   public String toSystem(V3CodingRationale code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CommunicationFunctionTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CommunicationFunctionTypeEnumFactory.java
index 2f30f82b36..a1c1e7ca7d 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CommunicationFunctionTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CommunicationFunctionTypeEnumFactory.java
@@ -48,14 +48,16 @@ public V3CommunicationFunctionType fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3CommunicationFunctionType code) {
-    if (code == V3CommunicationFunctionType.RCV)
+       if (code == V3CommunicationFunctionType.NULL)
+           return null;
+       if (code == V3CommunicationFunctionType.RCV)
       return "RCV";
     if (code == V3CommunicationFunctionType.RSP)
       return "RSP";
     if (code == V3CommunicationFunctionType.SND)
       return "SND";
     return "?";
-  }
+   }
 
   public String toSystem(V3CommunicationFunctionType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CompressionAlgorithmEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CompressionAlgorithmEnumFactory.java
index f155c6a197..ad5e6bc0d8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CompressionAlgorithmEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3CompressionAlgorithmEnumFactory.java
@@ -54,7 +54,9 @@ public V3CompressionAlgorithm fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3CompressionAlgorithm code) {
-    if (code == V3CompressionAlgorithm.BZ)
+       if (code == V3CompressionAlgorithm.NULL)
+           return null;
+       if (code == V3CompressionAlgorithm.BZ)
       return "BZ";
     if (code == V3CompressionAlgorithm.DF)
       return "DF";
@@ -67,7 +69,7 @@ public String toCode(V3CompressionAlgorithm code) {
     if (code == V3CompressionAlgorithm.ZL)
       return "ZL";
     return "?";
-  }
+   }
 
   public String toSystem(V3CompressionAlgorithm code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ConfidentialityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ConfidentialityEnumFactory.java
index f24cabce85..e18930f6f2 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ConfidentialityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ConfidentialityEnumFactory.java
@@ -82,7 +82,9 @@ public V3Confidentiality fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3Confidentiality code) {
-    if (code == V3Confidentiality._CONFIDENTIALITY)
+       if (code == V3Confidentiality.NULL)
+           return null;
+       if (code == V3Confidentiality._CONFIDENTIALITY)
       return "_Confidentiality";
     if (code == V3Confidentiality.L)
       return "L";
@@ -123,7 +125,7 @@ public String toCode(V3Confidentiality code) {
     if (code == V3Confidentiality.T)
       return "T";
     return "?";
-  }
+   }
 
   public String toSystem(V3Confidentiality code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerCapEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerCapEnumFactory.java
index 6b2fe61287..8b58ed467f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerCapEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerCapEnumFactory.java
@@ -56,7 +56,9 @@ public V3ContainerCap fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3ContainerCap code) {
-    if (code == V3ContainerCap._MEDICATIONCAP)
+       if (code == V3ContainerCap.NULL)
+           return null;
+       if (code == V3ContainerCap._MEDICATIONCAP)
       return "_MedicationCap";
     if (code == V3ContainerCap.CHILD)
       return "CHILD";
@@ -71,7 +73,7 @@ public String toCode(V3ContainerCap code) {
     if (code == V3ContainerCap.SCR)
       return "SCR";
     return "?";
-  }
+   }
 
   public String toSystem(V3ContainerCap code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerSeparatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerSeparatorEnumFactory.java
index 48f94b044d..6a0438143a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerSeparatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContainerSeparatorEnumFactory.java
@@ -46,12 +46,14 @@ public V3ContainerSeparator fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(V3ContainerSeparator code) {
-    if (code == V3ContainerSeparator.GEL)
+       if (code == V3ContainerSeparator.NULL)
+           return null;
+       if (code == V3ContainerSeparator.GEL)
       return "GEL";
     if (code == V3ContainerSeparator.NONE)
       return "NONE";
     return "?";
-  }
+   }
 
   public String toSystem(V3ContainerSeparator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContentProcessingModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContentProcessingModeEnumFactory.java
index 4658e2565b..3ec6f59fda 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContentProcessingModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContentProcessingModeEnumFactory.java
@@ -46,12 +46,14 @@ public V3ContentProcessingMode fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3ContentProcessingMode code) {
-    if (code == V3ContentProcessingMode.SEQL)
+       if (code == V3ContentProcessingMode.NULL)
+           return null;
+       if (code == V3ContentProcessingMode.SEQL)
       return "SEQL";
     if (code == V3ContentProcessingMode.UNOR)
       return "UNOR";
     return "?";
-  }
+   }
 
   public String toSystem(V3ContentProcessingMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContextControlEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContextControlEnumFactory.java
index 2c82297aec..945de4e261 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContextControlEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ContextControlEnumFactory.java
@@ -58,7 +58,9 @@ public V3ContextControl fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3ContextControl code) {
-    if (code == V3ContextControl._CONTEXTCONTROLADDITIVE)
+       if (code == V3ContextControl.NULL)
+           return null;
+       if (code == V3ContextControl._CONTEXTCONTROLADDITIVE)
       return "_ContextControlAdditive";
     if (code == V3ContextControl.AN)
       return "AN";
@@ -75,7 +77,7 @@ public String toCode(V3ContextControl code) {
     if (code == V3ContextControl._CONTEXTCONTROLPROPAGATING)
       return "_ContextControlPropagating";
     return "?";
-  }
+   }
 
   public String toSystem(V3ContextControl code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DataOperationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DataOperationEnumFactory.java
index 077ddb46b3..1161b5ada4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DataOperationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DataOperationEnumFactory.java
@@ -82,7 +82,9 @@ public V3DataOperation fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3DataOperation code) {
-    if (code == V3DataOperation.OPERATE)
+       if (code == V3DataOperation.NULL)
+           return null;
+       if (code == V3DataOperation.OPERATE)
       return "OPERATE";
     if (code == V3DataOperation.CREATE)
       return "CREATE";
@@ -123,7 +125,7 @@ public String toCode(V3DataOperation code) {
     if (code == V3DataOperation.SUSPEND)
       return "SUSPEND";
     return "?";
-  }
+   }
 
   public String toSystem(V3DataOperation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DeviceAlertLevelEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DeviceAlertLevelEnumFactory.java
index ac1f08bb37..b87f068f10 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DeviceAlertLevelEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DeviceAlertLevelEnumFactory.java
@@ -50,7 +50,9 @@ public V3DeviceAlertLevel fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3DeviceAlertLevel code) {
-    if (code == V3DeviceAlertLevel.C)
+       if (code == V3DeviceAlertLevel.NULL)
+           return null;
+       if (code == V3DeviceAlertLevel.C)
       return "C";
     if (code == V3DeviceAlertLevel.N)
       return "N";
@@ -59,7 +61,7 @@ public String toCode(V3DeviceAlertLevel code) {
     if (code == V3DeviceAlertLevel.W)
       return "W";
     return "?";
-  }
+   }
 
   public String toSystem(V3DeviceAlertLevel code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentCompletionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentCompletionEnumFactory.java
index 19baeef557..1b07fe0da9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentCompletionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentCompletionEnumFactory.java
@@ -60,7 +60,9 @@ public V3DocumentCompletion fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(V3DocumentCompletion code) {
-    if (code == V3DocumentCompletion.AU)
+       if (code == V3DocumentCompletion.NULL)
+           return null;
+       if (code == V3DocumentCompletion.AU)
       return "AU";
     if (code == V3DocumentCompletion.DI)
       return "DI";
@@ -79,7 +81,7 @@ public String toCode(V3DocumentCompletion code) {
     if (code == V3DocumentCompletion.UC)
       return "UC";
     return "?";
-  }
+   }
 
   public String toSystem(V3DocumentCompletion code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentStorageEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentStorageEnumFactory.java
index b71244fa74..acb25afe73 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentStorageEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3DocumentStorageEnumFactory.java
@@ -50,7 +50,9 @@ public V3DocumentStorage fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3DocumentStorage code) {
-    if (code == V3DocumentStorage.AC)
+       if (code == V3DocumentStorage.NULL)
+           return null;
+       if (code == V3DocumentStorage.AC)
       return "AC";
     if (code == V3DocumentStorage.AA)
       return "AA";
@@ -59,7 +61,7 @@ public String toCode(V3DocumentStorage code) {
     if (code == V3DocumentStorage.PU)
       return "PU";
     return "?";
-  }
+   }
 
   public String toSystem(V3DocumentStorage code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EducationLevelEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EducationLevelEnumFactory.java
index 22cf78793d..00fb6c2c47 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EducationLevelEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EducationLevelEnumFactory.java
@@ -60,7 +60,9 @@ public V3EducationLevel fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3EducationLevel code) {
-    if (code == V3EducationLevel.ASSOC)
+       if (code == V3EducationLevel.NULL)
+           return null;
+       if (code == V3EducationLevel.ASSOC)
       return "ASSOC";
     if (code == V3EducationLevel.BD)
       return "BD";
@@ -79,7 +81,7 @@ public String toCode(V3EducationLevel code) {
     if (code == V3EducationLevel.SEC)
       return "SEC";
     return "?";
-  }
+   }
 
   public String toSystem(V3EducationLevel code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EmployeeJobClassEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EmployeeJobClassEnumFactory.java
index fc9e8f9b81..58c1e82ab4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EmployeeJobClassEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EmployeeJobClassEnumFactory.java
@@ -46,12 +46,14 @@ public V3EmployeeJobClass fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3EmployeeJobClass code) {
-    if (code == V3EmployeeJobClass.FT)
+       if (code == V3EmployeeJobClass.NULL)
+           return null;
+       if (code == V3EmployeeJobClass.FT)
       return "FT";
     if (code == V3EmployeeJobClass.PT)
       return "PT";
     return "?";
-  }
+   }
 
   public String toSystem(V3EmployeeJobClass code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterAdmissionSourceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterAdmissionSourceEnumFactory.java
index 4ba026596e..28bd2fdd24 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterAdmissionSourceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterAdmissionSourceEnumFactory.java
@@ -48,14 +48,16 @@ public V3EncounterAdmissionSource fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(V3EncounterAdmissionSource code) {
-    if (code == V3EncounterAdmissionSource.E)
+       if (code == V3EncounterAdmissionSource.NULL)
+           return null;
+       if (code == V3EncounterAdmissionSource.E)
       return "E";
     if (code == V3EncounterAdmissionSource.LD)
       return "LD";
     if (code == V3EncounterAdmissionSource.NB)
       return "NB";
     return "?";
-  }
+   }
 
   public String toSystem(V3EncounterAdmissionSource code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterSpecialCourtesyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterSpecialCourtesyEnumFactory.java
index a9fd59725f..db612bf67c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterSpecialCourtesyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EncounterSpecialCourtesyEnumFactory.java
@@ -52,7 +52,9 @@ public V3EncounterSpecialCourtesy fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(V3EncounterSpecialCourtesy code) {
-    if (code == V3EncounterSpecialCourtesy.EXT)
+       if (code == V3EncounterSpecialCourtesy.NULL)
+           return null;
+       if (code == V3EncounterSpecialCourtesy.EXT)
       return "EXT";
     if (code == V3EncounterSpecialCourtesy.NRM)
       return "NRM";
@@ -63,7 +65,7 @@ public String toCode(V3EncounterSpecialCourtesy code) {
     if (code == V3EncounterSpecialCourtesy.VIP)
       return "VIP";
     return "?";
-  }
+   }
 
   public String toSystem(V3EncounterSpecialCourtesy code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityClassEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityClassEnumFactory.java
index 1e4c18a822..cd0ac940f4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityClassEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityClassEnumFactory.java
@@ -96,7 +96,9 @@ public V3EntityClass fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3EntityClass code) {
-    if (code == V3EntityClass.ENT)
+       if (code == V3EntityClass.NULL)
+           return null;
+       if (code == V3EntityClass.ENT)
       return "ENT";
     if (code == V3EntityClass.HCE)
       return "HCE";
@@ -151,7 +153,7 @@ public String toCode(V3EntityClass code) {
     if (code == V3EntityClass.RGRP)
       return "RGRP";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityClass code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityCodeEnumFactory.java
index 336dc09fd0..9cd3ff214f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityCodeEnumFactory.java
@@ -332,7 +332,9 @@ public V3EntityCode fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3EntityCode code) {
-    if (code == V3EntityCode._MATERIALENTITYCLASSTYPE)
+       if (code == V3EntityCode.NULL)
+           return null;
+       if (code == V3EntityCode._MATERIALENTITYCLASSTYPE)
       return "_MaterialEntityClassType";
     if (code == V3EntityCode._CONTAINERENTITYTYPE)
       return "_ContainerEntityType";
@@ -623,7 +625,7 @@ public String toCode(V3EntityCode code) {
     if (code == V3EntityCode.PRAC)
       return "PRAC";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityDeterminerEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityDeterminerEnumFactory.java
index 1daf56d4fb..32a2906887 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityDeterminerEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityDeterminerEnumFactory.java
@@ -52,7 +52,9 @@ public V3EntityDeterminer fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3EntityDeterminer code) {
-    if (code == V3EntityDeterminer.INSTANCE)
+       if (code == V3EntityDeterminer.NULL)
+           return null;
+       if (code == V3EntityDeterminer.INSTANCE)
       return "INSTANCE";
     if (code == V3EntityDeterminer.GROUP)
       return "GROUP";
@@ -63,7 +65,7 @@ public String toCode(V3EntityDeterminer code) {
     if (code == V3EntityDeterminer.QUANTIFIEDKIND)
       return "QUANTIFIED_KIND";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityDeterminer code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityHandlingEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityHandlingEnumFactory.java
index 95a31a3a05..28f4779859 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityHandlingEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityHandlingEnumFactory.java
@@ -78,7 +78,9 @@ public V3EntityHandling fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3EntityHandling code) {
-    if (code == V3EntityHandling.AMB)
+       if (code == V3EntityHandling.NULL)
+           return null;
+       if (code == V3EntityHandling.AMB)
       return "AMB";
     if (code == V3EntityHandling.C37)
       return "C37";
@@ -115,7 +117,7 @@ public String toCode(V3EntityHandling code) {
     if (code == V3EntityHandling.UPR)
       return "UPR";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityHandling code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierEnumFactory.java
index 7bacbb90e0..ffec0c7110 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierEnumFactory.java
@@ -100,7 +100,9 @@ public V3EntityNamePartQualifier fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(V3EntityNamePartQualifier code) {
-    if (code == V3EntityNamePartQualifier._ORGANIZATIONNAMEPARTQUALIFIER)
+       if (code == V3EntityNamePartQualifier.NULL)
+           return null;
+       if (code == V3EntityNamePartQualifier._ORGANIZATIONNAMEPARTQUALIFIER)
       return "_OrganizationNamePartQualifier";
     if (code == V3EntityNamePartQualifier.AC)
       return "AC";
@@ -159,7 +161,7 @@ public String toCode(V3EntityNamePartQualifier code) {
     if (code == V3EntityNamePartQualifier._PERSONNAMEPARTMISCQUALIFIER)
       return "_PersonNamePartMiscQualifier";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNamePartQualifier code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierR2EnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierR2EnumFactory.java
index 315a1e5f8f..bef5ddd640 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierR2EnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartQualifierR2EnumFactory.java
@@ -96,7 +96,9 @@ public V3EntityNamePartQualifierR2 fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3EntityNamePartQualifierR2 code) {
-    if (code == V3EntityNamePartQualifierR2.AD)
+       if (code == V3EntityNamePartQualifierR2.NULL)
+           return null;
+       if (code == V3EntityNamePartQualifierR2.AD)
       return "AD";
     if (code == V3EntityNamePartQualifierR2.SP)
       return "SP";
@@ -151,7 +153,7 @@ public String toCode(V3EntityNamePartQualifierR2 code) {
     if (code == V3EntityNamePartQualifierR2.PR)
       return "PR";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNamePartQualifierR2 code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeEnumFactory.java
index 50e5025ddf..f9e38b5fc5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeEnumFactory.java
@@ -52,7 +52,9 @@ public V3EntityNamePartType fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(V3EntityNamePartType code) {
-    if (code == V3EntityNamePartType.DEL)
+       if (code == V3EntityNamePartType.NULL)
+           return null;
+       if (code == V3EntityNamePartType.DEL)
       return "DEL";
     if (code == V3EntityNamePartType.FAM)
       return "FAM";
@@ -63,7 +65,7 @@ public String toCode(V3EntityNamePartType code) {
     if (code == V3EntityNamePartType.SFX)
       return "SFX";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNamePartType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeR2EnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeR2EnumFactory.java
index dc6ee82603..815b562fb6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeR2EnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNamePartTypeR2EnumFactory.java
@@ -50,7 +50,9 @@ public V3EntityNamePartTypeR2 fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3EntityNamePartTypeR2 code) {
-    if (code == V3EntityNamePartTypeR2.DEL)
+       if (code == V3EntityNamePartTypeR2.NULL)
+           return null;
+       if (code == V3EntityNamePartTypeR2.DEL)
       return "DEL";
     if (code == V3EntityNamePartTypeR2.FAM)
       return "FAM";
@@ -59,7 +61,7 @@ public String toCode(V3EntityNamePartTypeR2 code) {
     if (code == V3EntityNamePartTypeR2.TITLE)
       return "TITLE";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNamePartTypeR2 code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseEnumFactory.java
index 4e56a62a80..d05b8eb911 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseEnumFactory.java
@@ -72,7 +72,9 @@ public V3EntityNameUse fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3EntityNameUse code) {
-    if (code == V3EntityNameUse._NAMEREPRESENTATIONUSE)
+       if (code == V3EntityNameUse.NULL)
+           return null;
+       if (code == V3EntityNameUse._NAMEREPRESENTATIONUSE)
       return "_NameRepresentationUse";
     if (code == V3EntityNameUse.ABC)
       return "ABC";
@@ -103,7 +105,7 @@ public String toCode(V3EntityNameUse code) {
     if (code == V3EntityNameUse.SNDX)
       return "SNDX";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNameUse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseR2EnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseR2EnumFactory.java
index 5f131dd426..db1f2893d9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseR2EnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityNameUseR2EnumFactory.java
@@ -78,7 +78,9 @@ public V3EntityNameUseR2 fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3EntityNameUseR2 code) {
-    if (code == V3EntityNameUseR2.ASSUMED)
+       if (code == V3EntityNameUseR2.NULL)
+           return null;
+       if (code == V3EntityNameUseR2.ASSUMED)
       return "Assumed";
     if (code == V3EntityNameUseR2.A)
       return "A";
@@ -115,7 +117,7 @@ public String toCode(V3EntityNameUseR2 code) {
     if (code == V3EntityNameUseR2.T)
       return "T";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityNameUseR2 code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityRiskEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityRiskEnumFactory.java
index b1eeb17a14..bc4daa962a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityRiskEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityRiskEnumFactory.java
@@ -64,7 +64,9 @@ public V3EntityRisk fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3EntityRisk code) {
-    if (code == V3EntityRisk.AGG)
+       if (code == V3EntityRisk.NULL)
+           return null;
+       if (code == V3EntityRisk.AGG)
       return "AGG";
     if (code == V3EntityRisk.BIO)
       return "BIO";
@@ -87,7 +89,7 @@ public String toCode(V3EntityRisk code) {
     if (code == V3EntityRisk.RAD)
       return "RAD";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityRisk code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityStatusEnumFactory.java
index 4c441e97f6..a3b10cea60 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EntityStatusEnumFactory.java
@@ -52,7 +52,9 @@ public V3EntityStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3EntityStatus code) {
-    if (code == V3EntityStatus.NORMAL)
+       if (code == V3EntityStatus.NULL)
+           return null;
+       if (code == V3EntityStatus.NORMAL)
       return "normal";
     if (code == V3EntityStatus.ACTIVE)
       return "active";
@@ -63,7 +65,7 @@ public String toCode(V3EntityStatus code) {
     if (code == V3EntityStatus.NULLIFIED)
       return "nullified";
     return "?";
-  }
+   }
 
   public String toSystem(V3EntityStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EquipmentAlertLevelEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EquipmentAlertLevelEnumFactory.java
index 751b270fe6..44914a527a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EquipmentAlertLevelEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EquipmentAlertLevelEnumFactory.java
@@ -50,7 +50,9 @@ public V3EquipmentAlertLevel fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3EquipmentAlertLevel code) {
-    if (code == V3EquipmentAlertLevel.C)
+       if (code == V3EquipmentAlertLevel.NULL)
+           return null;
+       if (code == V3EquipmentAlertLevel.C)
       return "C";
     if (code == V3EquipmentAlertLevel.N)
       return "N";
@@ -59,7 +61,7 @@ public String toCode(V3EquipmentAlertLevel code) {
     if (code == V3EquipmentAlertLevel.W)
       return "W";
     return "?";
-  }
+   }
 
   public String toSystem(V3EquipmentAlertLevel code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EthnicityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EthnicityEnumFactory.java
index 93578c4f12..91007a5da3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EthnicityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3EthnicityEnumFactory.java
@@ -128,7 +128,9 @@ public V3Ethnicity fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3Ethnicity code) {
-    if (code == V3Ethnicity._21352)
+       if (code == V3Ethnicity.NULL)
+           return null;
+       if (code == V3Ethnicity._21352)
       return "2135-2";
     if (code == V3Ethnicity._21378)
       return "2137-8";
@@ -215,7 +217,7 @@ public String toCode(V3Ethnicity code) {
     if (code == V3Ethnicity._21865)
       return "2186-5";
     return "?";
-  }
+   }
 
   public String toSystem(V3Ethnicity code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ExposureModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ExposureModeEnumFactory.java
index 8019aa8fcc..fe0e93d357 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ExposureModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ExposureModeEnumFactory.java
@@ -52,7 +52,9 @@ public V3ExposureMode fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3ExposureMode code) {
-    if (code == V3ExposureMode._EXPOSUREMODE)
+       if (code == V3ExposureMode.NULL)
+           return null;
+       if (code == V3ExposureMode._EXPOSUREMODE)
       return "_ExposureMode";
     if (code == V3ExposureMode.AIRBORNE)
       return "AIRBORNE";
@@ -63,7 +65,7 @@ public String toCode(V3ExposureMode code) {
     if (code == V3ExposureMode.WATERBORNE)
       return "WATERBORNE";
     return "?";
-  }
+   }
 
   public String toSystem(V3ExposureMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GTSAbbreviationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GTSAbbreviationEnumFactory.java
index b2650e692f..a5cc52adf5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GTSAbbreviationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GTSAbbreviationEnumFactory.java
@@ -116,7 +116,9 @@ public V3GTSAbbreviation fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3GTSAbbreviation code) {
-    if (code == V3GTSAbbreviation.AM)
+       if (code == V3GTSAbbreviation.NULL)
+           return null;
+       if (code == V3GTSAbbreviation.AM)
       return "AM";
     if (code == V3GTSAbbreviation.BID)
       return "BID";
@@ -191,7 +193,7 @@ public String toCode(V3GTSAbbreviation code) {
     if (code == V3GTSAbbreviation.TID)
       return "TID";
     return "?";
-  }
+   }
 
   public String toSystem(V3GTSAbbreviation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GenderStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GenderStatusEnumFactory.java
index cd91ede027..b17c5f5469 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GenderStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3GenderStatusEnumFactory.java
@@ -46,12 +46,14 @@ public V3GenderStatus fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3GenderStatus code) {
-    if (code == V3GenderStatus.I)
+       if (code == V3GenderStatus.NULL)
+           return null;
+       if (code == V3GenderStatus.I)
       return "I";
     if (code == V3GenderStatus.N)
       return "N";
     return "?";
-  }
+   }
 
   public String toSystem(V3GenderStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HL7UpdateModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HL7UpdateModeEnumFactory.java
index 742587a24d..7b37a23b43 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HL7UpdateModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HL7UpdateModeEnumFactory.java
@@ -74,7 +74,9 @@ public V3HL7UpdateMode fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3HL7UpdateMode code) {
-    if (code == V3HL7UpdateMode.A)
+       if (code == V3HL7UpdateMode.NULL)
+           return null;
+       if (code == V3HL7UpdateMode.A)
       return "A";
     if (code == V3HL7UpdateMode.AR)
       return "AR";
@@ -107,7 +109,7 @@ public String toCode(V3HL7UpdateMode code) {
     if (code == V3HL7UpdateMode.V)
       return "V";
     return "?";
-  }
+   }
 
   public String toSystem(V3HL7UpdateMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7RealmEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7RealmEnumFactory.java
index 77ac0f8e19..4613104cfe 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7RealmEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7RealmEnumFactory.java
@@ -132,7 +132,9 @@ public V3Hl7Realm fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3Hl7Realm code) {
-    if (code == V3Hl7Realm.BINDINGREALMS)
+       if (code == V3Hl7Realm.NULL)
+           return null;
+       if (code == V3Hl7Realm.BINDINGREALMS)
       return "BindingRealms";
     if (code == V3Hl7Realm.AFFILIATEREALMS)
       return "AffiliateRealms";
@@ -223,7 +225,7 @@ public String toCode(V3Hl7Realm code) {
     if (code == V3Hl7Realm.ZZ)
       return "ZZ";
     return "?";
-  }
+   }
 
   public String toSystem(V3Hl7Realm code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7V3ConformanceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7V3ConformanceEnumFactory.java
index d147074085..d41d61d5bd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7V3ConformanceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3Hl7V3ConformanceEnumFactory.java
@@ -54,7 +54,9 @@ public V3Hl7V3Conformance fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3Hl7V3Conformance code) {
-    if (code == V3Hl7V3Conformance.I)
+       if (code == V3Hl7V3Conformance.NULL)
+           return null;
+       if (code == V3Hl7V3Conformance.I)
       return "I";
     if (code == V3Hl7V3Conformance.NP)
       return "NP";
@@ -67,7 +69,7 @@ public String toCode(V3Hl7V3Conformance code) {
     if (code == V3Hl7V3Conformance.U)
       return "U";
     return "?";
-  }
+   }
 
   public String toSystem(V3Hl7V3Conformance code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HtmlLinkTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HtmlLinkTypeEnumFactory.java
index 3a169ab540..2bff965dea 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HtmlLinkTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3HtmlLinkTypeEnumFactory.java
@@ -72,7 +72,9 @@ public V3HtmlLinkType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3HtmlLinkType code) {
-    if (code == V3HtmlLinkType.ALTERNATE)
+       if (code == V3HtmlLinkType.NULL)
+           return null;
+       if (code == V3HtmlLinkType.ALTERNATE)
       return "alternate";
     if (code == V3HtmlLinkType.APPENDIX)
       return "appendix";
@@ -103,7 +105,7 @@ public String toCode(V3HtmlLinkType code) {
     if (code == V3HtmlLinkType.SUBSECTION)
       return "subsection";
     return "?";
-  }
+   }
 
   public String toSystem(V3HtmlLinkType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierReliabilityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierReliabilityEnumFactory.java
index c6198ebdb7..22a4c94ed0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierReliabilityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierReliabilityEnumFactory.java
@@ -48,14 +48,16 @@ public V3IdentifierReliability fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3IdentifierReliability code) {
-    if (code == V3IdentifierReliability.ISS)
+       if (code == V3IdentifierReliability.NULL)
+           return null;
+       if (code == V3IdentifierReliability.ISS)
       return "ISS";
     if (code == V3IdentifierReliability.UNV)
       return "UNV";
     if (code == V3IdentifierReliability.VRF)
       return "VRF";
     return "?";
-  }
+   }
 
   public String toSystem(V3IdentifierReliability code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierScopeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierScopeEnumFactory.java
index 5df0b208f1..d6612ef572 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierScopeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IdentifierScopeEnumFactory.java
@@ -50,7 +50,9 @@ public V3IdentifierScope fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3IdentifierScope code) {
-    if (code == V3IdentifierScope.BUSN)
+       if (code == V3IdentifierScope.NULL)
+           return null;
+       if (code == V3IdentifierScope.BUSN)
       return "BUSN";
     if (code == V3IdentifierScope.OBJ)
       return "OBJ";
@@ -59,7 +61,7 @@ public String toCode(V3IdentifierScope code) {
     if (code == V3IdentifierScope.VW)
       return "VW";
     return "?";
-  }
+   }
 
   public String toSystem(V3IdentifierScope code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IntegrityCheckAlgorithmEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IntegrityCheckAlgorithmEnumFactory.java
index f685d48591..100330654a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IntegrityCheckAlgorithmEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3IntegrityCheckAlgorithmEnumFactory.java
@@ -46,12 +46,14 @@ public V3IntegrityCheckAlgorithm fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(V3IntegrityCheckAlgorithm code) {
-    if (code == V3IntegrityCheckAlgorithm.SHA1)
+       if (code == V3IntegrityCheckAlgorithm.NULL)
+           return null;
+       if (code == V3IntegrityCheckAlgorithm.SHA1)
       return "SHA-1";
     if (code == V3IntegrityCheckAlgorithm.SHA256)
       return "SHA-256";
     return "?";
-  }
+   }
 
   public String toSystem(V3IntegrityCheckAlgorithm code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityModeEnumFactory.java
index fc7111211c..41670dfcf6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityModeEnumFactory.java
@@ -54,7 +54,9 @@ public V3LanguageAbilityMode fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3LanguageAbilityMode code) {
-    if (code == V3LanguageAbilityMode.ESGN)
+       if (code == V3LanguageAbilityMode.NULL)
+           return null;
+       if (code == V3LanguageAbilityMode.ESGN)
       return "ESGN";
     if (code == V3LanguageAbilityMode.ESP)
       return "ESP";
@@ -67,7 +69,7 @@ public String toCode(V3LanguageAbilityMode code) {
     if (code == V3LanguageAbilityMode.RWR)
       return "RWR";
     return "?";
-  }
+   }
 
   public String toSystem(V3LanguageAbilityMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityProficiencyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityProficiencyEnumFactory.java
index bc9e863c1c..0a9779de96 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityProficiencyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LanguageAbilityProficiencyEnumFactory.java
@@ -50,7 +50,9 @@ public V3LanguageAbilityProficiency fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(V3LanguageAbilityProficiency code) {
-    if (code == V3LanguageAbilityProficiency.E)
+       if (code == V3LanguageAbilityProficiency.NULL)
+           return null;
+       if (code == V3LanguageAbilityProficiency.E)
       return "E";
     if (code == V3LanguageAbilityProficiency.F)
       return "F";
@@ -59,7 +61,7 @@ public String toCode(V3LanguageAbilityProficiency code) {
     if (code == V3LanguageAbilityProficiency.P)
       return "P";
     return "?";
-  }
+   }
 
   public String toSystem(V3LanguageAbilityProficiency code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LivingArrangementEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LivingArrangementEnumFactory.java
index cee972bdf9..deba5d82ae 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LivingArrangementEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LivingArrangementEnumFactory.java
@@ -66,7 +66,9 @@ public V3LivingArrangement fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3LivingArrangement code) {
-    if (code == V3LivingArrangement.HL)
+       if (code == V3LivingArrangement.NULL)
+           return null;
+       if (code == V3LivingArrangement.HL)
       return "HL";
     if (code == V3LivingArrangement.M)
       return "M";
@@ -91,7 +93,7 @@ public String toCode(V3LivingArrangement code) {
     if (code == V3LivingArrangement.SL)
       return "SL";
     return "?";
-  }
+   }
 
   public String toSystem(V3LivingArrangement code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalMarkupIgnoreEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalMarkupIgnoreEnumFactory.java
index df4bf508e4..aabc2a75d3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalMarkupIgnoreEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalMarkupIgnoreEnumFactory.java
@@ -46,12 +46,14 @@ public V3LocalMarkupIgnore fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3LocalMarkupIgnore code) {
-    if (code == V3LocalMarkupIgnore.ALL)
+       if (code == V3LocalMarkupIgnore.NULL)
+           return null;
+       if (code == V3LocalMarkupIgnore.ALL)
       return "all";
     if (code == V3LocalMarkupIgnore.MARKUP)
       return "markup";
     return "?";
-  }
+   }
 
   public String toSystem(V3LocalMarkupIgnore code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalRemoteControlStateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalRemoteControlStateEnumFactory.java
index 014a132e29..091ba2e8bd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalRemoteControlStateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3LocalRemoteControlStateEnumFactory.java
@@ -46,12 +46,14 @@ public V3LocalRemoteControlState fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(V3LocalRemoteControlState code) {
-    if (code == V3LocalRemoteControlState.L)
+       if (code == V3LocalRemoteControlState.NULL)
+           return null;
+       if (code == V3LocalRemoteControlState.L)
       return "L";
     if (code == V3LocalRemoteControlState.R)
       return "R";
     return "?";
-  }
+   }
 
   public String toSystem(V3LocalRemoteControlState code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ManagedParticipationStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ManagedParticipationStatusEnumFactory.java
index 4413c18e22..3697a1571c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ManagedParticipationStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ManagedParticipationStatusEnumFactory.java
@@ -54,7 +54,9 @@ public V3ManagedParticipationStatus fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(V3ManagedParticipationStatus code) {
-    if (code == V3ManagedParticipationStatus.NORMAL)
+       if (code == V3ManagedParticipationStatus.NULL)
+           return null;
+       if (code == V3ManagedParticipationStatus.NORMAL)
       return "normal";
     if (code == V3ManagedParticipationStatus.ACTIVE)
       return "active";
@@ -67,7 +69,7 @@ public String toCode(V3ManagedParticipationStatus code) {
     if (code == V3ManagedParticipationStatus.NULLIFIED)
       return "nullified";
     return "?";
-  }
+   }
 
   public String toSystem(V3ManagedParticipationStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MapRelationshipEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MapRelationshipEnumFactory.java
index f9c9e1335e..32e6470a8a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MapRelationshipEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MapRelationshipEnumFactory.java
@@ -48,14 +48,16 @@ public V3MapRelationship fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3MapRelationship code) {
-    if (code == V3MapRelationship.BT)
+       if (code == V3MapRelationship.NULL)
+           return null;
+       if (code == V3MapRelationship.BT)
       return "BT";
     if (code == V3MapRelationship.E)
       return "E";
     if (code == V3MapRelationship.NT)
       return "NT";
     return "?";
-  }
+   }
 
   public String toSystem(V3MapRelationship code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MaritalStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MaritalStatusEnumFactory.java
index f803bf986c..8e360a585b 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MaritalStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MaritalStatusEnumFactory.java
@@ -62,7 +62,9 @@ public V3MaritalStatus fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3MaritalStatus code) {
-    if (code == V3MaritalStatus.A)
+       if (code == V3MaritalStatus.NULL)
+           return null;
+       if (code == V3MaritalStatus.A)
       return "A";
     if (code == V3MaritalStatus.D)
       return "D";
@@ -83,7 +85,7 @@ public String toCode(V3MaritalStatus code) {
     if (code == V3MaritalStatus.W)
       return "W";
     return "?";
-  }
+   }
 
   public String toSystem(V3MaritalStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MessageWaitingPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MessageWaitingPriorityEnumFactory.java
index f12ed8229e..be02da6e04 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MessageWaitingPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3MessageWaitingPriorityEnumFactory.java
@@ -48,14 +48,16 @@ public V3MessageWaitingPriority fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(V3MessageWaitingPriority code) {
-    if (code == V3MessageWaitingPriority.H)
+       if (code == V3MessageWaitingPriority.NULL)
+           return null;
+       if (code == V3MessageWaitingPriority.H)
       return "H";
     if (code == V3MessageWaitingPriority.L)
       return "L";
     if (code == V3MessageWaitingPriority.M)
       return "M";
     return "?";
-  }
+   }
 
   public String toSystem(V3MessageWaitingPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ModifyIndicatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ModifyIndicatorEnumFactory.java
index e90c5b6b5e..4362970c1f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ModifyIndicatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ModifyIndicatorEnumFactory.java
@@ -46,12 +46,14 @@ public V3ModifyIndicator fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3ModifyIndicator code) {
-    if (code == V3ModifyIndicator.M)
+       if (code == V3ModifyIndicator.NULL)
+           return null;
+       if (code == V3ModifyIndicator.M)
       return "M";
     if (code == V3ModifyIndicator.N)
       return "N";
     return "?";
-  }
+   }
 
   public String toSystem(V3ModifyIndicator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3NullFlavorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3NullFlavorEnumFactory.java
index 85ea4e00d6..e091cd94b4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3NullFlavorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3NullFlavorEnumFactory.java
@@ -76,7 +76,9 @@ public V3NullFlavor fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3NullFlavor code) {
-    if (code == V3NullFlavor.NI)
+       if (code == V3NullFlavor.NULL)
+           return null;
+       if (code == V3NullFlavor.NI)
       return "NI";
     if (code == V3NullFlavor.INV)
       return "INV";
@@ -111,7 +113,7 @@ public String toCode(V3NullFlavor code) {
     if (code == V3NullFlavor.NP)
       return "NP";
     return "?";
-  }
+   }
 
   public String toSystem(V3NullFlavor code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationInterpretationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationInterpretationEnumFactory.java
index 0e26cfbc6e..d2c3188fb0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationInterpretationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationInterpretationEnumFactory.java
@@ -150,7 +150,9 @@ public V3ObservationInterpretation fromCode(String codeString) throws IllegalArg
   }
 
   public String toCode(V3ObservationInterpretation code) {
-    if (code == V3ObservationInterpretation._GENETICOBSERVATIONINTERPRETATION)
+       if (code == V3ObservationInterpretation.NULL)
+           return null;
+       if (code == V3ObservationInterpretation._GENETICOBSERVATIONINTERPRETATION)
       return "_GeneticObservationInterpretation";
     if (code == V3ObservationInterpretation.CAR)
       return "CAR";
@@ -259,7 +261,7 @@ public String toCode(V3ObservationInterpretation code) {
     if (code == V3ObservationInterpretation.WR)
       return "WR";
     return "?";
-  }
+   }
 
   public String toSystem(V3ObservationInterpretation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationMethodEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationMethodEnumFactory.java
index 53e20b972d..6b688801d4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationMethodEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationMethodEnumFactory.java
@@ -650,7 +650,9 @@ public V3ObservationMethod fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3ObservationMethod code) {
-    if (code == V3ObservationMethod._DECISIONOBSERVATIONMETHOD)
+       if (code == V3ObservationMethod.NULL)
+           return null;
+       if (code == V3ObservationMethod._DECISIONOBSERVATIONMETHOD)
       return "_DecisionObservationMethod";
     if (code == V3ObservationMethod.ALGM)
       return "ALGM";
@@ -1259,7 +1261,7 @@ public String toCode(V3ObservationMethod code) {
     if (code == V3ObservationMethod._0127)
       return "0127";
     return "?";
-  }
+   }
 
   public String toSystem(V3ObservationMethod code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationValueEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationValueEnumFactory.java
index 5970907f91..0869816632 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationValueEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ObservationValueEnumFactory.java
@@ -498,7 +498,9 @@ public V3ObservationValue fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3ObservationValue code) {
-    if (code == V3ObservationValue._ACTCOVERAGEASSESSMENTOBSERVATIONVALUE)
+       if (code == V3ObservationValue.NULL)
+           return null;
+       if (code == V3ObservationValue._ACTCOVERAGEASSESSMENTOBSERVATIONVALUE)
       return "_ActCoverageAssessmentObservationValue";
     if (code == V3ObservationValue._ACTFINANCIALSTATUSOBSERVATIONVALUE)
       return "_ActFinancialStatusObservationValue";
@@ -955,7 +957,7 @@ public String toCode(V3ObservationValue code) {
     if (code == V3ObservationValue._INDICATIONVALUE)
       return "_IndicationValue";
     return "?";
-  }
+   }
 
   public String toSystem(V3ObservationValue code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3OrderableDrugFormEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3OrderableDrugFormEnumFactory.java
index ca532c6e2b..99a403169c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3OrderableDrugFormEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3OrderableDrugFormEnumFactory.java
@@ -364,7 +364,9 @@ public V3OrderableDrugForm fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3OrderableDrugForm code) {
-    if (code == V3OrderableDrugForm._ADMINISTRABLEDRUGFORM)
+       if (code == V3OrderableDrugForm.NULL)
+           return null;
+       if (code == V3OrderableDrugForm._ADMINISTRABLEDRUGFORM)
       return "_AdministrableDrugForm";
     if (code == V3OrderableDrugForm.APPFUL)
       return "APPFUL";
@@ -687,7 +689,7 @@ public String toCode(V3OrderableDrugForm code) {
     if (code == V3OrderableDrugForm.WAFER)
       return "WAFER";
     return "?";
-  }
+   }
 
   public String toSystem(V3OrderableDrugForm code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationFunctionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationFunctionEnumFactory.java
index ecbb107266..8af0f4e508 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationFunctionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationFunctionEnumFactory.java
@@ -140,7 +140,9 @@ public V3ParticipationFunction fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3ParticipationFunction code) {
-    if (code == V3ParticipationFunction._AUTHORIZEDPARTICIPATIONFUNCTION)
+       if (code == V3ParticipationFunction.NULL)
+           return null;
+       if (code == V3ParticipationFunction._AUTHORIZEDPARTICIPATIONFUNCTION)
       return "_AuthorizedParticipationFunction";
     if (code == V3ParticipationFunction._AUTHORIZEDRECEIVERPARTICIPATIONFUNCTION)
       return "_AuthorizedReceiverParticipationFunction";
@@ -239,7 +241,7 @@ public String toCode(V3ParticipationFunction code) {
     if (code == V3ParticipationFunction.TASST)
       return "TASST";
     return "?";
-  }
+   }
 
   public String toSystem(V3ParticipationFunction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationModeEnumFactory.java
index 556d056bf8..deb5dc3019 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationModeEnumFactory.java
@@ -72,7 +72,9 @@ public V3ParticipationMode fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3ParticipationMode code) {
-    if (code == V3ParticipationMode.ELECTRONIC)
+       if (code == V3ParticipationMode.NULL)
+           return null;
+       if (code == V3ParticipationMode.ELECTRONIC)
       return "ELECTRONIC";
     if (code == V3ParticipationMode.PHYSICAL)
       return "PHYSICAL";
@@ -103,7 +105,7 @@ public String toCode(V3ParticipationMode code) {
     if (code == V3ParticipationMode.TYPEWRIT)
       return "TYPEWRIT";
     return "?";
-  }
+   }
 
   public String toSystem(V3ParticipationMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationSignatureEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationSignatureEnumFactory.java
index 76cf56a6a4..4db2147167 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationSignatureEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationSignatureEnumFactory.java
@@ -48,14 +48,16 @@ public V3ParticipationSignature fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(V3ParticipationSignature code) {
-    if (code == V3ParticipationSignature.I)
+       if (code == V3ParticipationSignature.NULL)
+           return null;
+       if (code == V3ParticipationSignature.I)
       return "I";
     if (code == V3ParticipationSignature.S)
       return "S";
     if (code == V3ParticipationSignature.X)
       return "X";
     return "?";
-  }
+   }
 
   public String toSystem(V3ParticipationSignature code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationTypeEnumFactory.java
index de1e4217f9..ee9d077252 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ParticipationTypeEnumFactory.java
@@ -164,7 +164,9 @@ public V3ParticipationType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3ParticipationType code) {
-    if (code == V3ParticipationType.PART)
+       if (code == V3ParticipationType.NULL)
+           return null;
+       if (code == V3ParticipationType.PART)
       return "PART";
     if (code == V3ParticipationType._PARTICIPATIONANCILLARY)
       return "_ParticipationAncillary";
@@ -287,7 +289,7 @@ public String toCode(V3ParticipationType code) {
     if (code == V3ParticipationType.LA)
       return "LA";
     return "?";
-  }
+   }
 
   public String toSystem(V3ParticipationType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PatientImportanceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PatientImportanceEnumFactory.java
index d8bf60d8c5..c1ad261274 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PatientImportanceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PatientImportanceEnumFactory.java
@@ -60,7 +60,9 @@ public V3PatientImportance fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3PatientImportance code) {
-    if (code == V3PatientImportance.BM)
+       if (code == V3PatientImportance.NULL)
+           return null;
+       if (code == V3PatientImportance.BM)
       return "BM";
     if (code == V3PatientImportance.DFM)
       return "DFM";
@@ -79,7 +81,7 @@ public String toCode(V3PatientImportance code) {
     if (code == V3PatientImportance.VIP)
       return "VIP";
     return "?";
-  }
+   }
 
   public String toSystem(V3PatientImportance code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PaymentTermsEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PaymentTermsEnumFactory.java
index e96c585fc7..0b0d320a86 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PaymentTermsEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PaymentTermsEnumFactory.java
@@ -50,7 +50,9 @@ public V3PaymentTerms fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3PaymentTerms code) {
-    if (code == V3PaymentTerms.COD)
+       if (code == V3PaymentTerms.NULL)
+           return null;
+       if (code == V3PaymentTerms.COD)
       return "COD";
     if (code == V3PaymentTerms.N30)
       return "N30";
@@ -59,7 +61,7 @@ public String toCode(V3PaymentTerms code) {
     if (code == V3PaymentTerms.N90)
       return "N90";
     return "?";
-  }
+   }
 
   public String toSystem(V3PaymentTerms code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PersonDisabilityTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PersonDisabilityTypeEnumFactory.java
index fcf9be1718..a565b4a8fd 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PersonDisabilityTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3PersonDisabilityTypeEnumFactory.java
@@ -62,7 +62,9 @@ public V3PersonDisabilityType fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3PersonDisabilityType code) {
-    if (code == V3PersonDisabilityType._1)
+       if (code == V3PersonDisabilityType.NULL)
+           return null;
+       if (code == V3PersonDisabilityType._1)
       return "1";
     if (code == V3PersonDisabilityType._2)
       return "2";
@@ -83,7 +85,7 @@ public String toCode(V3PersonDisabilityType code) {
     if (code == V3PersonDisabilityType.WK)
       return "WK";
     return "?";
-  }
+   }
 
   public String toSystem(V3PersonDisabilityType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProbabilityDistributionTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProbabilityDistributionTypeEnumFactory.java
index ea22ca1272..212aa694ba 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProbabilityDistributionTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProbabilityDistributionTypeEnumFactory.java
@@ -60,7 +60,9 @@ public V3ProbabilityDistributionType fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(V3ProbabilityDistributionType code) {
-    if (code == V3ProbabilityDistributionType.B)
+       if (code == V3ProbabilityDistributionType.NULL)
+           return null;
+       if (code == V3ProbabilityDistributionType.B)
       return "B";
     if (code == V3ProbabilityDistributionType.E)
       return "E";
@@ -79,7 +81,7 @@ public String toCode(V3ProbabilityDistributionType code) {
     if (code == V3ProbabilityDistributionType.X2)
       return "X2";
     return "?";
-  }
+   }
 
   public String toSystem(V3ProbabilityDistributionType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingIDEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingIDEnumFactory.java
index b9a54d436b..aee48543ac 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingIDEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingIDEnumFactory.java
@@ -48,14 +48,16 @@ public V3ProcessingID fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3ProcessingID code) {
-    if (code == V3ProcessingID.D)
+       if (code == V3ProcessingID.NULL)
+           return null;
+       if (code == V3ProcessingID.D)
       return "D";
     if (code == V3ProcessingID.P)
       return "P";
     if (code == V3ProcessingID.T)
       return "T";
     return "?";
-  }
+   }
 
   public String toSystem(V3ProcessingID code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingModeEnumFactory.java
index 47788f9434..607472d7f9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ProcessingModeEnumFactory.java
@@ -50,7 +50,9 @@ public V3ProcessingMode fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3ProcessingMode code) {
-    if (code == V3ProcessingMode.A)
+       if (code == V3ProcessingMode.NULL)
+           return null;
+       if (code == V3ProcessingMode.A)
       return "A";
     if (code == V3ProcessingMode.I)
       return "I";
@@ -59,7 +61,7 @@ public String toCode(V3ProcessingMode code) {
     if (code == V3ProcessingMode.T)
       return "T";
     return "?";
-  }
+   }
 
   public String toSystem(V3ProcessingMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryParameterValueEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryParameterValueEnumFactory.java
index 4db9eba4fc..91570bae66 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryParameterValueEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryParameterValueEnumFactory.java
@@ -74,7 +74,9 @@ public V3QueryParameterValue fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3QueryParameterValue code) {
-    if (code == V3QueryParameterValue._DISPENSEQUERYFILTERCODE)
+       if (code == V3QueryParameterValue.NULL)
+           return null;
+       if (code == V3QueryParameterValue._DISPENSEQUERYFILTERCODE)
       return "_DispenseQueryFilterCode";
     if (code == V3QueryParameterValue.ALLDISP)
       return "ALLDISP";
@@ -107,7 +109,7 @@ public String toCode(V3QueryParameterValue code) {
     if (code == V3QueryParameterValue.ISSFU)
       return "ISSFU";
     return "?";
-  }
+   }
 
   public String toSystem(V3QueryParameterValue code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryPriorityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryPriorityEnumFactory.java
index 0ad06b1719..f081016a7c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryPriorityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryPriorityEnumFactory.java
@@ -46,12 +46,14 @@ public V3QueryPriority fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3QueryPriority code) {
-    if (code == V3QueryPriority.D)
+       if (code == V3QueryPriority.NULL)
+           return null;
+       if (code == V3QueryPriority.D)
       return "D";
     if (code == V3QueryPriority.I)
       return "I";
     return "?";
-  }
+   }
 
   public String toSystem(V3QueryPriority code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryRequestLimitEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryRequestLimitEnumFactory.java
index b091bd709e..1e56f84c93 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryRequestLimitEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryRequestLimitEnumFactory.java
@@ -46,12 +46,14 @@ public V3QueryRequestLimit fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(V3QueryRequestLimit code) {
-    if (code == V3QueryRequestLimit._QUERYREQUESTLIMIT)
+       if (code == V3QueryRequestLimit.NULL)
+           return null;
+       if (code == V3QueryRequestLimit._QUERYREQUESTLIMIT)
       return "_QueryRequestLimit";
     if (code == V3QueryRequestLimit.RD)
       return "RD";
     return "?";
-  }
+   }
 
   public String toSystem(V3QueryRequestLimit code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryResponseEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryResponseEnumFactory.java
index 1333b885a7..b356dd735a 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryResponseEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryResponseEnumFactory.java
@@ -50,7 +50,9 @@ public V3QueryResponse fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3QueryResponse code) {
-    if (code == V3QueryResponse.AE)
+       if (code == V3QueryResponse.NULL)
+           return null;
+       if (code == V3QueryResponse.AE)
       return "AE";
     if (code == V3QueryResponse.NF)
       return "NF";
@@ -59,7 +61,7 @@ public String toCode(V3QueryResponse code) {
     if (code == V3QueryResponse.QE)
       return "QE";
     return "?";
-  }
+   }
 
   public String toSystem(V3QueryResponse code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryStatusCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryStatusCodeEnumFactory.java
index 04ef621c8a..c147a614f3 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryStatusCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3QueryStatusCodeEnumFactory.java
@@ -52,7 +52,9 @@ public V3QueryStatusCode fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3QueryStatusCode code) {
-    if (code == V3QueryStatusCode.ABORTED)
+       if (code == V3QueryStatusCode.NULL)
+           return null;
+       if (code == V3QueryStatusCode.ABORTED)
       return "aborted";
     if (code == V3QueryStatusCode.DELIVEREDRESPONSE)
       return "deliveredResponse";
@@ -63,7 +65,7 @@ public String toCode(V3QueryStatusCode code) {
     if (code == V3QueryStatusCode.WAITCONTINUEDQUERYRESPONSE)
       return "waitContinuedQueryResponse";
     return "?";
-  }
+   }
 
   public String toSystem(V3QueryStatusCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RaceEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RaceEnumFactory.java
index 78b3171967..3b4dcf58d5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RaceEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RaceEnumFactory.java
@@ -1884,7 +1884,9 @@ public V3Race fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3Race code) {
-    if (code == V3Race._10025)
+       if (code == V3Race.NULL)
+           return null;
+       if (code == V3Race._10025)
       return "1002-5";
     if (code == V3Race._10041)
       return "1004-1";
@@ -3727,7 +3729,7 @@ public String toCode(V3Race code) {
     if (code == V3Race._21311)
       return "2131-1";
     return "?";
-  }
+   }
 
   public String toSystem(V3Race code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationalOperatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationalOperatorEnumFactory.java
index 959ace26c1..eefe9e6403 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationalOperatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationalOperatorEnumFactory.java
@@ -58,7 +58,9 @@ public V3RelationalOperator fromCode(String codeString) throws IllegalArgumentEx
   }
 
   public String toCode(V3RelationalOperator code) {
-    if (code == V3RelationalOperator.CT)
+       if (code == V3RelationalOperator.NULL)
+           return null;
+       if (code == V3RelationalOperator.CT)
       return "CT";
     if (code == V3RelationalOperator.EQ)
       return "EQ";
@@ -75,7 +77,7 @@ public String toCode(V3RelationalOperator code) {
     if (code == V3RelationalOperator.NE)
       return "NE";
     return "?";
-  }
+   }
 
   public String toSystem(V3RelationalOperator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationshipConjunctionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationshipConjunctionEnumFactory.java
index dc93b71b44..63793609f9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationshipConjunctionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RelationshipConjunctionEnumFactory.java
@@ -48,14 +48,16 @@ public V3RelationshipConjunction fromCode(String codeString) throws IllegalArgum
   }
 
   public String toCode(V3RelationshipConjunction code) {
-    if (code == V3RelationshipConjunction.AND)
+       if (code == V3RelationshipConjunction.NULL)
+           return null;
+       if (code == V3RelationshipConjunction.AND)
       return "AND";
     if (code == V3RelationshipConjunction.OR)
       return "OR";
     if (code == V3RelationshipConjunction.XOR)
       return "XOR";
     return "?";
-  }
+   }
 
   public String toSystem(V3RelationshipConjunction code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ReligiousAffiliationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ReligiousAffiliationEnumFactory.java
index 0d5c00812c..0fd50caaa5 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ReligiousAffiliationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ReligiousAffiliationEnumFactory.java
@@ -206,7 +206,9 @@ public V3ReligiousAffiliation fromCode(String codeString) throws IllegalArgument
   }
 
   public String toCode(V3ReligiousAffiliation code) {
-    if (code == V3ReligiousAffiliation._1001)
+       if (code == V3ReligiousAffiliation.NULL)
+           return null;
+       if (code == V3ReligiousAffiliation._1001)
       return "1001";
     if (code == V3ReligiousAffiliation._1002)
       return "1002";
@@ -371,7 +373,7 @@ public String toCode(V3ReligiousAffiliation code) {
     if (code == V3ReligiousAffiliation._1082)
       return "1082";
     return "?";
-  }
+   }
 
   public String toSystem(V3ReligiousAffiliation code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseLevelEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseLevelEnumFactory.java
index 4a7a23fcc5..ea6c3240b0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseLevelEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseLevelEnumFactory.java
@@ -56,7 +56,9 @@ public V3ResponseLevel fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(V3ResponseLevel code) {
-    if (code == V3ResponseLevel.C)
+       if (code == V3ResponseLevel.NULL)
+           return null;
+       if (code == V3ResponseLevel.C)
       return "C";
     if (code == V3ResponseLevel.D)
       return "D";
@@ -71,7 +73,7 @@ public String toCode(V3ResponseLevel code) {
     if (code == V3ResponseLevel.X)
       return "X";
     return "?";
-  }
+   }
 
   public String toSystem(V3ResponseLevel code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModalityEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModalityEnumFactory.java
index 0bdb74534e..a4a3672618 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModalityEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModalityEnumFactory.java
@@ -48,14 +48,16 @@ public V3ResponseModality fromCode(String codeString) throws IllegalArgumentExce
   }
 
   public String toCode(V3ResponseModality code) {
-    if (code == V3ResponseModality.B)
+       if (code == V3ResponseModality.NULL)
+           return null;
+       if (code == V3ResponseModality.B)
       return "B";
     if (code == V3ResponseModality.R)
       return "R";
     if (code == V3ResponseModality.T)
       return "T";
     return "?";
-  }
+   }
 
   public String toSystem(V3ResponseModality code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModeEnumFactory.java
index 6010bb8230..2b96577178 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3ResponseModeEnumFactory.java
@@ -48,14 +48,16 @@ public V3ResponseMode fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3ResponseMode code) {
-    if (code == V3ResponseMode.D)
+       if (code == V3ResponseMode.NULL)
+           return null;
+       if (code == V3ResponseMode.D)
       return "D";
     if (code == V3ResponseMode.I)
       return "I";
     if (code == V3ResponseMode.Q)
       return "Q";
     return "?";
-  }
+   }
 
   public String toSystem(V3ResponseMode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleClassEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleClassEnumFactory.java
index 5a8c93311d..747d5ae6ff 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleClassEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleClassEnumFactory.java
@@ -266,7 +266,9 @@ public V3RoleClass fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3RoleClass code) {
-    if (code == V3RoleClass.ROL)
+       if (code == V3RoleClass.NULL)
+           return null;
+       if (code == V3RoleClass.ROL)
       return "ROL";
     if (code == V3RoleClass._ROLECLASSASSOCIATIVE)
       return "_RoleClassAssociative";
@@ -491,7 +493,7 @@ public String toCode(V3RoleClass code) {
     if (code == V3RoleClass.PHYS)
       return "PHYS";
     return "?";
-  }
+   }
 
   public String toSystem(V3RoleClass code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleCodeEnumFactory.java
index a898b950ac..32f1f4b000 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleCodeEnumFactory.java
@@ -836,7 +836,9 @@ public V3RoleCode fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(V3RoleCode code) {
-    if (code == V3RoleCode._AFFILIATIONROLETYPE)
+       if (code == V3RoleCode.NULL)
+           return null;
+       if (code == V3RoleCode._AFFILIATIONROLETYPE)
       return "_AffiliationRoleType";
     if (code == V3RoleCode._AGENTROLETYPE)
       return "_AgentRoleType";
@@ -1631,7 +1633,7 @@ public String toCode(V3RoleCode code) {
     if (code == V3RoleCode.SUBSCR)
       return "SUBSCR";
     return "?";
-  }
+   }
 
   public String toSystem(V3RoleCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkStatusEnumFactory.java
index 163cecae70..63997b59f0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkStatusEnumFactory.java
@@ -54,7 +54,9 @@ public V3RoleLinkStatus fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3RoleLinkStatus code) {
-    if (code == V3RoleLinkStatus.NORMAL)
+       if (code == V3RoleLinkStatus.NULL)
+           return null;
+       if (code == V3RoleLinkStatus.NORMAL)
       return "NORMAL";
     if (code == V3RoleLinkStatus.ACTIVE)
       return "ACTIVE";
@@ -67,7 +69,7 @@ public String toCode(V3RoleLinkStatus code) {
     if (code == V3RoleLinkStatus.NULLIFIED)
       return "NULLIFIED";
     return "?";
-  }
+   }
 
   public String toSystem(V3RoleLinkStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkTypeEnumFactory.java
index 109c2b4bfd..be0826b0ec 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleLinkTypeEnumFactory.java
@@ -58,7 +58,9 @@ public V3RoleLinkType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3RoleLinkType code) {
-    if (code == V3RoleLinkType.REL)
+       if (code == V3RoleLinkType.NULL)
+           return null;
+       if (code == V3RoleLinkType.REL)
       return "REL";
     if (code == V3RoleLinkType.BACKUP)
       return "BACKUP";
@@ -75,7 +77,7 @@ public String toCode(V3RoleLinkType code) {
     if (code == V3RoleLinkType.REPL)
       return "REPL";
     return "?";
-  }
+   }
 
   public String toSystem(V3RoleLinkType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleStatusEnumFactory.java
index 06d7ec3491..a24dd5e8e8 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RoleStatusEnumFactory.java
@@ -56,7 +56,9 @@ public V3RoleStatus fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3RoleStatus code) {
-    if (code == V3RoleStatus.NORMAL)
+       if (code == V3RoleStatus.NULL)
+           return null;
+       if (code == V3RoleStatus.NORMAL)
       return "normal";
     if (code == V3RoleStatus.ACTIVE)
       return "active";
@@ -71,7 +73,7 @@ public String toCode(V3RoleStatus code) {
     if (code == V3RoleStatus.NULLIFIED)
       return "nullified";
     return "?";
-  }
+   }
 
   public String toSystem(V3RoleStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RouteOfAdministrationEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RouteOfAdministrationEnumFactory.java
index eadd1f633e..aefe57ccf0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RouteOfAdministrationEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3RouteOfAdministrationEnumFactory.java
@@ -814,7 +814,9 @@ public V3RouteOfAdministration fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3RouteOfAdministration code) {
-    if (code == V3RouteOfAdministration._ROUTEBYMETHOD)
+       if (code == V3RouteOfAdministration.NULL)
+           return null;
+       if (code == V3RouteOfAdministration._ROUTEBYMETHOD)
       return "_RouteByMethod";
     if (code == V3RouteOfAdministration.SOAK)
       return "SOAK";
@@ -1587,7 +1589,7 @@ public String toCode(V3RouteOfAdministration code) {
     if (code == V3RouteOfAdministration._VITREOUSHUMOURROUTE)
       return "_VitreousHumourRoute";
     return "?";
-  }
+   }
 
   public String toSystem(V3RouteOfAdministration code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SequencingEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SequencingEnumFactory.java
index fb7df3872b..ba43214344 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SequencingEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SequencingEnumFactory.java
@@ -48,14 +48,16 @@ public V3Sequencing fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3Sequencing code) {
-    if (code == V3Sequencing.A)
+       if (code == V3Sequencing.NULL)
+           return null;
+       if (code == V3Sequencing.A)
       return "A";
     if (code == V3Sequencing.D)
       return "D";
     if (code == V3Sequencing.N)
       return "N";
     return "?";
-  }
+   }
 
   public String toSystem(V3Sequencing code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SetOperatorEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SetOperatorEnumFactory.java
index fbf50b76a8..b36cc1924e 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SetOperatorEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SetOperatorEnumFactory.java
@@ -54,7 +54,9 @@ public V3SetOperator fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3SetOperator code) {
-    if (code == V3SetOperator._VALUESETOPERATOR)
+       if (code == V3SetOperator.NULL)
+           return null;
+       if (code == V3SetOperator._VALUESETOPERATOR)
       return "_ValueSetOperator";
     if (code == V3SetOperator.E)
       return "E";
@@ -67,7 +69,7 @@ public String toCode(V3SetOperator code) {
     if (code == V3SetOperator.P)
       return "P";
     return "?";
-  }
+   }
 
   public String toSystem(V3SetOperator code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SpecimenTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SpecimenTypeEnumFactory.java
index bdc56a3921..845dee68e6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SpecimenTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SpecimenTypeEnumFactory.java
@@ -290,7 +290,9 @@ public V3SpecimenType fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(V3SpecimenType code) {
-    if (code == V3SpecimenType._SPECIMENENTITYTYPE)
+       if (code == V3SpecimenType.NULL)
+           return null;
+       if (code == V3SpecimenType._SPECIMENENTITYTYPE)
       return "_SpecimenEntityType";
     if (code == V3SpecimenType.ABS)
       return "ABS";
@@ -539,7 +541,7 @@ public String toCode(V3SpecimenType code) {
     if (code == V3SpecimenType.WNDE)
       return "WNDE";
     return "?";
-  }
+   }
 
   public String toSystem(V3SpecimenType code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstanceAdminSubstitutionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstanceAdminSubstitutionEnumFactory.java
index 582fa31cfe..d9913784a9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstanceAdminSubstitutionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstanceAdminSubstitutionEnumFactory.java
@@ -62,7 +62,9 @@ public V3SubstanceAdminSubstitution fromCode(String codeString) throws IllegalAr
   }
 
   public String toCode(V3SubstanceAdminSubstitution code) {
-    if (code == V3SubstanceAdminSubstitution._ACTSUBSTANCEADMINSUBSTITUTIONCODE)
+       if (code == V3SubstanceAdminSubstitution.NULL)
+           return null;
+       if (code == V3SubstanceAdminSubstitution._ACTSUBSTANCEADMINSUBSTITUTIONCODE)
       return "_ActSubstanceAdminSubstitutionCode";
     if (code == V3SubstanceAdminSubstitution.E)
       return "E";
@@ -83,7 +85,7 @@ public String toCode(V3SubstanceAdminSubstitution code) {
     if (code == V3SubstanceAdminSubstitution.N)
       return "N";
     return "?";
-  }
+   }
 
   public String toSystem(V3SubstanceAdminSubstitution code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstitutionConditionEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstitutionConditionEnumFactory.java
index faf7a92072..43dfc60409 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstitutionConditionEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3SubstitutionConditionEnumFactory.java
@@ -52,7 +52,9 @@ public V3SubstitutionCondition fromCode(String codeString) throws IllegalArgumen
   }
 
   public String toCode(V3SubstitutionCondition code) {
-    if (code == V3SubstitutionCondition._CONDITIONAL)
+       if (code == V3SubstitutionCondition.NULL)
+           return null;
+       if (code == V3SubstitutionCondition._CONDITIONAL)
       return "_Conditional";
     if (code == V3SubstitutionCondition.CONFIRM)
       return "CONFIRM";
@@ -63,7 +65,7 @@ public String toCode(V3SubstitutionCondition code) {
     if (code == V3SubstitutionCondition.UNCOND)
       return "UNCOND";
     return "?";
-  }
+   }
 
   public String toSystem(V3SubstitutionCondition code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellHorizontalAlignEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellHorizontalAlignEnumFactory.java
index c9ae5961e7..c0d9c1edf0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellHorizontalAlignEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellHorizontalAlignEnumFactory.java
@@ -52,7 +52,9 @@ public V3TableCellHorizontalAlign fromCode(String codeString) throws IllegalArgu
   }
 
   public String toCode(V3TableCellHorizontalAlign code) {
-    if (code == V3TableCellHorizontalAlign.CENTER)
+       if (code == V3TableCellHorizontalAlign.NULL)
+           return null;
+       if (code == V3TableCellHorizontalAlign.CENTER)
       return "center";
     if (code == V3TableCellHorizontalAlign.CHAR)
       return "char";
@@ -63,7 +65,7 @@ public String toCode(V3TableCellHorizontalAlign code) {
     if (code == V3TableCellHorizontalAlign.RIGHT)
       return "right";
     return "?";
-  }
+   }
 
   public String toSystem(V3TableCellHorizontalAlign code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellScopeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellScopeEnumFactory.java
index 93709791e4..0c83291ca9 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellScopeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellScopeEnumFactory.java
@@ -50,7 +50,9 @@ public V3TableCellScope fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3TableCellScope code) {
-    if (code == V3TableCellScope.COL)
+       if (code == V3TableCellScope.NULL)
+           return null;
+       if (code == V3TableCellScope.COL)
       return "col";
     if (code == V3TableCellScope.COLGROUP)
       return "colgroup";
@@ -59,7 +61,7 @@ public String toCode(V3TableCellScope code) {
     if (code == V3TableCellScope.ROWGROUP)
       return "rowgroup";
     return "?";
-  }
+   }
 
   public String toSystem(V3TableCellScope code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellVerticalAlignEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellVerticalAlignEnumFactory.java
index a18cf5914e..d003e05b58 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellVerticalAlignEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableCellVerticalAlignEnumFactory.java
@@ -50,7 +50,9 @@ public V3TableCellVerticalAlign fromCode(String codeString) throws IllegalArgume
   }
 
   public String toCode(V3TableCellVerticalAlign code) {
-    if (code == V3TableCellVerticalAlign.BASELINE)
+       if (code == V3TableCellVerticalAlign.NULL)
+           return null;
+       if (code == V3TableCellVerticalAlign.BASELINE)
       return "baseline";
     if (code == V3TableCellVerticalAlign.BOTTOM)
       return "bottom";
@@ -59,7 +61,7 @@ public String toCode(V3TableCellVerticalAlign code) {
     if (code == V3TableCellVerticalAlign.TOP)
       return "top";
     return "?";
-  }
+   }
 
   public String toSystem(V3TableCellVerticalAlign code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableFrameEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableFrameEnumFactory.java
index 7b6dec3047..49bf5890be 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableFrameEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableFrameEnumFactory.java
@@ -60,7 +60,9 @@ public V3TableFrame fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3TableFrame code) {
-    if (code == V3TableFrame.ABOVE)
+       if (code == V3TableFrame.NULL)
+           return null;
+       if (code == V3TableFrame.ABOVE)
       return "above";
     if (code == V3TableFrame.BELOW)
       return "below";
@@ -79,7 +81,7 @@ public String toCode(V3TableFrame code) {
     if (code == V3TableFrame.VSIDES)
       return "vsides";
     return "?";
-  }
+   }
 
   public String toSystem(V3TableFrame code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableRulesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableRulesEnumFactory.java
index 6c2db98dd2..81614adeb0 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableRulesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TableRulesEnumFactory.java
@@ -52,7 +52,9 @@ public V3TableRules fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3TableRules code) {
-    if (code == V3TableRules.ALL)
+       if (code == V3TableRules.NULL)
+           return null;
+       if (code == V3TableRules.ALL)
       return "all";
     if (code == V3TableRules.COLS)
       return "cols";
@@ -63,7 +65,7 @@ public String toCode(V3TableRules code) {
     if (code == V3TableRules.ROWS)
       return "rows";
     return "?";
-  }
+   }
 
   public String toSystem(V3TableRules code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TargetAwarenessEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TargetAwarenessEnumFactory.java
index 12cc002402..a24ab8c109 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TargetAwarenessEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TargetAwarenessEnumFactory.java
@@ -54,7 +54,9 @@ public V3TargetAwareness fromCode(String codeString) throws IllegalArgumentExcep
   }
 
   public String toCode(V3TargetAwareness code) {
-    if (code == V3TargetAwareness.D)
+       if (code == V3TargetAwareness.NULL)
+           return null;
+       if (code == V3TargetAwareness.D)
       return "D";
     if (code == V3TargetAwareness.F)
       return "F";
@@ -67,7 +69,7 @@ public String toCode(V3TargetAwareness code) {
     if (code == V3TargetAwareness.U)
       return "U";
     return "?";
-  }
+   }
 
   public String toSystem(V3TargetAwareness code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TelecommunicationCapabilitiesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TelecommunicationCapabilitiesEnumFactory.java
index b7a283a18e..e2e5e70202 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TelecommunicationCapabilitiesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TelecommunicationCapabilitiesEnumFactory.java
@@ -52,7 +52,9 @@ public V3TelecommunicationCapabilities fromCode(String codeString) throws Illega
   }
 
   public String toCode(V3TelecommunicationCapabilities code) {
-    if (code == V3TelecommunicationCapabilities.DATA)
+       if (code == V3TelecommunicationCapabilities.NULL)
+           return null;
+       if (code == V3TelecommunicationCapabilities.DATA)
       return "data";
     if (code == V3TelecommunicationCapabilities.FAX)
       return "fax";
@@ -63,7 +65,7 @@ public String toCode(V3TelecommunicationCapabilities code) {
     if (code == V3TelecommunicationCapabilities.VOICE)
       return "voice";
     return "?";
-  }
+   }
 
   public String toSystem(V3TelecommunicationCapabilities code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TimingEventEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TimingEventEnumFactory.java
index b769c6be02..d5c194bb7c 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TimingEventEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TimingEventEnumFactory.java
@@ -78,7 +78,9 @@ public V3TimingEvent fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(V3TimingEvent code) {
-    if (code == V3TimingEvent.AC)
+       if (code == V3TimingEvent.NULL)
+           return null;
+       if (code == V3TimingEvent.AC)
       return "AC";
     if (code == V3TimingEvent.ACD)
       return "ACD";
@@ -115,7 +117,7 @@ public String toCode(V3TimingEvent code) {
     if (code == V3TimingEvent.WAKE)
       return "WAKE";
     return "?";
-  }
+   }
 
   public String toSystem(V3TimingEvent code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TransmissionRelationshipTypeCodeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TransmissionRelationshipTypeCodeEnumFactory.java
index 4ffb84aeb5..628bf6d219 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TransmissionRelationshipTypeCodeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TransmissionRelationshipTypeCodeEnumFactory.java
@@ -44,10 +44,12 @@ public V3TransmissionRelationshipTypeCode fromCode(String codeString) throws Ill
   }
 
   public String toCode(V3TransmissionRelationshipTypeCode code) {
-    if (code == V3TransmissionRelationshipTypeCode.SEQL)
+       if (code == V3TransmissionRelationshipTypeCode.NULL)
+           return null;
+       if (code == V3TransmissionRelationshipTypeCode.SEQL)
       return "SEQL";
     return "?";
-  }
+   }
 
   public String toSystem(V3TransmissionRelationshipTypeCode code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TribalEntityUSEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TribalEntityUSEnumFactory.java
index 09a63a86df..e827241168 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TribalEntityUSEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3TribalEntityUSEnumFactory.java
@@ -1178,7 +1178,9 @@ public V3TribalEntityUS fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(V3TribalEntityUS code) {
-    if (code == V3TribalEntityUS._NATIVEENTITYALASKA)
+       if (code == V3TribalEntityUS.NULL)
+           return null;
+       if (code == V3TribalEntityUS._NATIVEENTITYALASKA)
       return "_NativeEntityAlaska";
     if (code == V3TribalEntityUS._338)
       return "338";
@@ -2315,7 +2317,7 @@ public String toCode(V3TribalEntityUS code) {
     if (code == V3TribalEntityUS._99)
       return "99";
     return "?";
-  }
+   }
 
   public String toSystem(V3TribalEntityUS code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3VaccineManufacturerEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3VaccineManufacturerEnumFactory.java
index 94e8fdbaad..98148484f6 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3VaccineManufacturerEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/V3VaccineManufacturerEnumFactory.java
@@ -122,7 +122,9 @@ public V3VaccineManufacturer fromCode(String codeString) throws IllegalArgumentE
   }
 
   public String toCode(V3VaccineManufacturer code) {
-    if (code == V3VaccineManufacturer.AB)
+       if (code == V3VaccineManufacturer.NULL)
+           return null;
+       if (code == V3VaccineManufacturer.AB)
       return "AB";
     if (code == V3VaccineManufacturer.AD)
       return "AD";
@@ -203,7 +205,7 @@ public String toCode(V3VaccineManufacturer code) {
     if (code == V3VaccineManufacturer.WAL)
       return "WAL";
     return "?";
-  }
+   }
 
   public String toSystem(V3VaccineManufacturer code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusEnumFactory.java
index 343ec9aace..058b36a660 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusEnumFactory.java
@@ -46,12 +46,14 @@ public VaccinationProtocolDoseStatus fromCode(String codeString) throws IllegalA
   }
 
   public String toCode(VaccinationProtocolDoseStatus code) {
-    if (code == VaccinationProtocolDoseStatus.COUNT)
+       if (code == VaccinationProtocolDoseStatus.NULL)
+           return null;
+       if (code == VaccinationProtocolDoseStatus.COUNT)
       return "count";
     if (code == VaccinationProtocolDoseStatus.NOCOUNT)
       return "nocount";
     return "?";
-  }
+   }
 
   public String toSystem(VaccinationProtocolDoseStatus code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusReasonEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusReasonEnumFactory.java
index 76c25b83a5..7af6650c75 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusReasonEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VaccinationProtocolDoseStatusReasonEnumFactory.java
@@ -53,7 +53,9 @@ public VaccinationProtocolDoseStatusReason fromCode(String codeString) throws Il
   }
 
   public String toCode(VaccinationProtocolDoseStatusReason code) {
-    if (code == VaccinationProtocolDoseStatusReason.ADVSTORAGE)
+       if (code == VaccinationProtocolDoseStatusReason.NULL)
+           return null;
+       if (code == VaccinationProtocolDoseStatusReason.ADVSTORAGE)
       return "advstorage";
     if (code == VaccinationProtocolDoseStatusReason.COLDCHBRK)
       return "coldchbrk";
@@ -64,7 +66,7 @@ public String toCode(VaccinationProtocolDoseStatusReason code) {
     if (code == VaccinationProtocolDoseStatusReason.PRODRECALL)
       return "prodrecall";
     return "?";
-  }
+   }
 
   public String toSystem(VaccinationProtocolDoseStatusReason code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ValueCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ValueCodesEnumFactory.java
index dd75f8fbd4..f90df399c7 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ValueCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/ValueCodesEnumFactory.java
@@ -46,12 +46,14 @@ public ValueCodes fromCode(String codeString) throws IllegalArgumentException {
   }
 
   public String toCode(ValueCodes code) {
-    if (code == ValueCodes._1001)
+       if (code == ValueCodes.NULL)
+           return null;
+       if (code == ValueCodes._1001)
       return "1001";
     if (code == ValueCodes._1002)
       return "1002";
     return "?";
-  }
+   }
 
   public String toSystem(ValueCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VariantStateEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VariantStateEnumFactory.java
index 064fa7e05d..d626b02b88 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VariantStateEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VariantStateEnumFactory.java
@@ -48,14 +48,16 @@ public VariantState fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(VariantState code) {
-    if (code == VariantState.POSITIVE)
+       if (code == VariantState.NULL)
+           return null;
+       if (code == VariantState.POSITIVE)
       return "positive";
     if (code == VariantState.NEGATIVE)
       return "negative";
     if (code == VariantState.ABSENT)
       return "absent";
     return "?";
-  }
+   }
 
   public String toSystem(VariantState code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VersioningPolicyEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VersioningPolicyEnumFactory.java
index 51aa106685..6cfa146eb4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VersioningPolicyEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VersioningPolicyEnumFactory.java
@@ -48,14 +48,16 @@ public VersioningPolicy fromCode(String codeString) throws IllegalArgumentExcept
   }
 
   public String toCode(VersioningPolicy code) {
-    if (code == VersioningPolicy.NOVERSION)
+       if (code == VersioningPolicy.NULL)
+           return null;
+       if (code == VersioningPolicy.NOVERSION)
       return "no-version";
     if (code == VersioningPolicy.VERSIONED)
       return "versioned";
     if (code == VersioningPolicy.VERSIONEDUPDATE)
       return "versioned-update";
     return "?";
-  }
+   }
 
   public String toSystem(VersioningPolicy code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionBaseCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionBaseCodesEnumFactory.java
index 54be066eba..400c510749 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionBaseCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionBaseCodesEnumFactory.java
@@ -50,7 +50,9 @@ public VisionBaseCodes fromCode(String codeString) throws IllegalArgumentExcepti
   }
 
   public String toCode(VisionBaseCodes code) {
-    if (code == VisionBaseCodes.UP)
+       if (code == VisionBaseCodes.NULL)
+           return null;
+       if (code == VisionBaseCodes.UP)
       return "up";
     if (code == VisionBaseCodes.DOWN)
       return "down";
@@ -59,7 +61,7 @@ public String toCode(VisionBaseCodes code) {
     if (code == VisionBaseCodes.OUT)
       return "out";
     return "?";
-  }
+   }
 
   public String toSystem(VisionBaseCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionEyeCodesEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionEyeCodesEnumFactory.java
index 11b9d31084..6929acbf59 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionEyeCodesEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionEyeCodesEnumFactory.java
@@ -46,12 +46,14 @@ public VisionEyeCodes fromCode(String codeString) throws IllegalArgumentExceptio
   }
 
   public String toCode(VisionEyeCodes code) {
-    if (code == VisionEyeCodes.RIGHT)
+       if (code == VisionEyeCodes.NULL)
+           return null;
+       if (code == VisionEyeCodes.RIGHT)
       return "right";
     if (code == VisionEyeCodes.LEFT)
       return "left";
     return "?";
-  }
+   }
 
   public String toSystem(VisionEyeCodes code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionProductEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionProductEnumFactory.java
index 6e13b9fbb1..324c6e4fe4 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionProductEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/VisionProductEnumFactory.java
@@ -46,12 +46,14 @@ public VisionProduct fromCode(String codeString) throws IllegalArgumentException
   }
 
   public String toCode(VisionProduct code) {
-    if (code == VisionProduct.LENS)
+       if (code == VisionProduct.NULL)
+           return null;
+       if (code == VisionProduct.LENS)
       return "lens";
     if (code == VisionProduct.CONTACT)
       return "contact";
     return "?";
-  }
+   }
 
   public String toSystem(VisionProduct code) {
     return code.getSystem();
diff --git a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/XdsRelationshipTypeEnumFactory.java b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/XdsRelationshipTypeEnumFactory.java
index 2c5bde2088..1795afc10f 100644
--- a/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/XdsRelationshipTypeEnumFactory.java
+++ b/org.hl7.fhir.dstu2016may/src/main/java/org/hl7/fhir/dstu2016may/model/codesystems/XdsRelationshipTypeEnumFactory.java
@@ -52,7 +52,9 @@ public XdsRelationshipType fromCode(String codeString) throws IllegalArgumentExc
   }
 
   public String toCode(XdsRelationshipType code) {
-    if (code == XdsRelationshipType.APND)
+       if (code == XdsRelationshipType.NULL)
+           return null;
+       if (code == XdsRelationshipType.APND)
       return "APND";
     if (code == XdsRelationshipType.RPLC)
       return "RPLC";
@@ -63,7 +65,7 @@ public String toCode(XdsRelationshipType code) {
     if (code == XdsRelationshipType.SIGNS)
       return "signs";
     return "?";
-  }
+   }
 
   public String toSystem(XdsRelationshipType code) {
     return code.getSystem();