Documentation update

input/images-source/component.plantuml

@@ -0,0 +1,47 @@
+@startuml
+
+
+interface "FHIR RESTful API" as api
+
+component "FHIR Validation" as validator
+note right
+HAPI FHIR Plain Server
+end note
+
+component "NHS England Terminology Server" as onto
+note right
+Used for validating SNOMED Terminology
+end note
+
+component "Inbuilt Terminology Server" as internal
+note right
+Pre loaded with FHIR Profiles, ValueSets
+and CodeSystems from supplied FHIR Packages
+end note
+
+interface "FHIR RESTful API" as Facade
+note right
+Facade which handles Onto Server
+authentication
+end note
+
+interface "FHIR RESTful API" as AWSFacade
+note right
+Facade which handles Cognito
+authentication
+end note
+
+component AWSFHIRWorks
+note right
+Repository of FHIR Questionnsaire's
+end note
+
+
+api -- validator
+validator -- Facade
+validator -- internal
+validator -- AWSFacade
+Facade -- onto
+AWSFacade -- AWSFHIRWorks
+
+@enduml

readme.md

@@ -33,3 +33,16 @@ The configuration is aimed at supporting different use cases. For example the la
 
 See [Environmental Variables](environment-variables.md) for configuration options.
 
+## Architecture
+
+The Validator is based on [HAPI FHIR Instance Validator](https://hapifhir.io/hapi-fhir/docs/validation/instance_validator.html), which is exposed using a [HAPI FHIR Plain Server](https://hapifhir.io/hapi-fhir/docs/server_plain/server_types.html) which gives an FHIR RESTful API to a [FHIR $validate operation](https://www.hl7.org/fhir/resource-operation-validate.html). 
+This API is documented via [OpenAPI Specification (swagger)](https://swagger.io/specification/) as part of the service [here](http://lb-fhir-validator-924628614.eu-west-2.elb.amazonaws.com/swagger-ui/index.html)  
+
+![validator component diagram](./input/images/component-diagram.png)
+
+Internally validation configuration is composed of: 
+
+- `DefaultProfileValidationSupport` - which includes base FHIR CodeSystems and ValueSets
+- `CommonCodeSystemsTerminologyService` - which includes UK Core and NHS England FHIR NPM packages
+- A customised version of `TerminologyServiceValidationSupport` to handle the security mechanism of NHS England's Terminology Server
+- `AWSValidationSupport` a custom class to enable validation of FHIR QuestionnaireResponse using FHIR Questionnaire's stored a AWS FHIRWorks server.