diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMAbout.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMAbout.scala
index 84f9b970c..07ff986a0 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMAbout.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMAbout.scala
@@ -24,6 +24,7 @@ with
     Serializable
 {
     implicit val session: SparkSession = spark
+    implicit val storage_level: StorageLevel = storage // for put()
     implicit val log: Logger = LoggerFactory.getLogger (getClass)
 
     /**
@@ -102,10 +103,7 @@ with
             val new_elements = element_groups.map (merge)
 
             // swap the old Elements RDD for the new one
-            elements.name = "about_Elements"
-            new_elements.name = "Elements"
-            new_elements.persist (storage)
-            if (spark.sparkContext.getCheckpointDir.isDefined) new_elements.checkpoint ()
+            put (new_elements, "Elements")
 
             new_elements
         }
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMDeDup.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMDeDup.scala
index 47daa244b..773cf87f2 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMDeDup.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMDeDup.scala
@@ -39,6 +39,7 @@ import ch.ninecode.model._
 class CIMDeDup (spark: SparkSession, storage: StorageLevel = StorageLevel.MEMORY_AND_DISK_SER) extends CIMRDD with Serializable
 {
     implicit val session: SparkSession = spark
+    implicit val storage_level: StorageLevel = storage // for put()
     implicit val log: Logger = LoggerFactory.getLogger (getClass)
 
     /**
@@ -72,11 +73,16 @@ class CIMDeDup (spark: SparkSession, storage: StorageLevel = StorageLevel.MEMORY
      */
     def deduplicate (elements: Iterable[Element]): Element =
     {
-        val ret = elements.head
-        if (1 != elements.size)
-            // check for equality
-            check (ret, elements.tail)
-        ret
+        elements.toList match
+        {
+            case head :: Nil =>
+                head
+            case head :: tail =>
+                // check for equality
+                check (head, tail)
+                head
+            case _ => BasicElement ()
+        }
     }
 
     /**
@@ -101,10 +107,7 @@ class CIMDeDup (spark: SparkSession, storage: StorageLevel = StorageLevel.MEMORY
         val new_elements = elements.keyBy (_.id).groupByKey ().values.map (deduplicate)
 
         // swap the old Elements RDD for the new one
-        elements.name = "duplicate_Elements"
-        new_elements.name = "Elements"
-        new_elements.persist (storage)
-        if (spark.sparkContext.getCheckpointDir.isDefined) new_elements.checkpoint ()
+        put (new_elements, "Elements")
 
         new_elements
     }
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMEdges.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMEdges.scala
index 79a77a8f1..1cddaab1d 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMEdges.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMEdges.scala
@@ -411,7 +411,7 @@ with Serializable
         val asseted_edges = located_edges.keyBy (_._1.id_equ).leftOuterJoin (assets.flatMap (psr)).map (x => (x._2._1._1, x._2._1._2, x._2._2))
 
         // join with topological nodes if requested
-        if (topological_nodes)
+        val _ = if (topological_nodes)
         {
             val topologicals = getOrElse[TopologicalNode].keyBy (_.id)
             val topo1 = asseted_edges.keyBy (_._1.cn_1).leftOuterJoin (topologicals).values.map (x => (x._1._1, x._1._2, x._1._3, x._2))
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMIntegrityChecker.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMIntegrityChecker.scala
index b476c4ffb..7c10ca08e 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMIntegrityChecker.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMIntegrityChecker.scala
@@ -52,20 +52,8 @@ class Worker[C <: Product, P <: Product] (relation: Relationship, child: String,
 
     def message (child: String, field: String, parent: String) (problem: (String, Product)): String =
     {
-        val (key, obj) = problem
-        new StringBuilder ()
-            .append (child)
-            .append (" ")
-            .append (primary_key (obj)) // equipment.id
-            .append (" field ")
-            .append (field)
-            .append (" ")
-            .append (" references ")
-            .append (parent)
-            .append (" ")
-            .append (key)
-            .append (" that is not present")
-            .toString
+        val (key: String, obj: Product) = problem
+        s"$child ${primary_key (obj)} field $field references $parent $key that is not present"
     }
 
     def run (): String =
@@ -104,33 +92,27 @@ class CIMIntegrityChecker (spark: SparkSession) extends CIMRDD with Serializable
         // val equipment: RDD[Equipment] = spark.sparkContext.getPersistentRDDs.filter (_._2.name == "Equipment").head._2.asInstanceOf[RDD[Equipment]]
 
         type childrdd = info.subsetter.rddtype
-        val companion: ClassInfo = classes.filter (_.name == relation.clazz).head
+        val companion: ClassInfo = classes.find (_.name == relation.clazz).getOrElse (ch.ninecode.model.Unknown.register)
         type parentrdd = companion.subsetter.rddtype
 
         if (log.isDebugEnabled)
             log.debug (s"${info.name}.${relation.field} => ${relation.clazz}")
-        val cc: collection.Map[Int, RDD[_]] = spark.sparkContext.getPersistentRDDs.filter (_._2.name == info.name)
-        if (cc.nonEmpty)
-        {
-            val ccc: childrdd = cc.head._2.asInstanceOf[childrdd]
-
-            //val container: RDD[EquipmentContainer] = spark.sparkContext.getPersistentRDDs.filter (_._2.name == "EquipmentContainer").head._2.asInstanceOf[RDD[EquipmentContainer]]
-            val pc: collection.Map[Int, RDD[_]] = spark.sparkContext.getPersistentRDDs.filter (_._2.name == companion.name)
-            if (pc.nonEmpty)
-            {
-                val pcc: parentrdd = pc.head._2.asInstanceOf[parentrdd]
-                val worker = new Worker (relation, info.name, ccc, companion.name, pcc)
-                worker.run ()
-            }
-            else
+        spark.sparkContext.getPersistentRDDs.find (_._2.name == info.name).map (x => x._2)
+            .fold ("")
             {
-                // every instance is an error
-                val worker = new Worker (relation, info.name, ccc, companion.name, null)
-                worker.run ()
+                case rdd: childrdd =>
+                    //val container: RDD[EquipmentContainer] = spark.sparkContext.getPersistentRDDs.filter (_._2.name == "EquipmentContainer").head._2.asInstanceOf[RDD[EquipmentContainer]]
+                    spark.sparkContext.getPersistentRDDs.find (_._2.name == companion.name).map (x => x._2)
+                        .fold (
+                            // every instance is an error
+                            new Worker (relation, info.name, rdd, companion.name, null).run ()
+                        )
+                    {
+                        case pcc: parentrdd =>
+                            new Worker (relation, info.name, rdd, companion.name, pcc).run ()
+                    }
             }
-        }
-        else
-            ""
+
     }
 
     def checkClass (classes: List[ClassInfo]) (info: ClassInfo): Option[String] =
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMJoin.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMJoin.scala
index d8cf91267..1eaa6ee3d 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMJoin.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMJoin.scala
@@ -299,10 +299,7 @@ class CIMJoin (spark: SparkSession, storage: StorageLevel) extends CIMRDD with S
                 )
 
         // swap the old Elements RDD for the new one
-        old_elements.name = "unjoined_Elements"
-        new_elements.name = "Elements"
-        new_elements.persist (storage)
-        if (spark.sparkContext.getCheckpointDir.isDefined) new_elements.checkpoint ()
+        put (new_elements, "Elements")
 
         new_elements
     }
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMNetworkTopologyProcessor.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMNetworkTopologyProcessor.scala
index c5664de4f..4a20bdf08 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMNetworkTopologyProcessor.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMNetworkTopologyProcessor.scala
@@ -356,14 +356,30 @@ case class CIMNetworkTopologyProcessor (spark: SparkSession) extends CIMRDD
         {
             // check for uniqueness of VertexId
             val duplicates = vertices.groupByKey.filter (_._2.size > 1)
-            if (!duplicates.isEmpty ())
-                duplicates.collect.map (x => { log.error (s"VertexId clash (${x._1}) for ${x._2.head.node_label} and ${x._2.tail.head.node_label}"); 1 })
+            duplicates.collect.foreach (
+                x =>
+                {
+                    val (vertex, data) = x
+                    data.toList match
+                    {
+                        case head :: tail :: Nil =>
+                            log.error (s"VertexId clash ($vertex) for ${head.node_label} and ${tail.node_label}")
+                        case _ =>
+                    }
+                }
+            )
 
             // check for missing vertices
             val cn = edges.flatMap (x => List ((x.attr.id_cn_1, x.attr.id_equ), (x.attr.id_cn_2, x.attr.id_equ)))
-            val missing = cn.leftOuterJoin (vertices.keyBy (_._2.node_label)).filter (_._2._2 match { case None => true case _ => false } ).map (x => (x._2._1, x._1))
-            if (!missing.isEmpty)
-                missing.collect.map (x => { log.error (s"${x._1} missing ConnectivityNode ${x._2}"); 1 })
+            val missing = cn.leftOuterJoin (vertices.keyBy (_._2.node_label))
+                .filter (_._2._2 match { case None => true case _ => false } ).map (x => (x._2._1, x._1))
+            missing.collect.foreach (
+                x =>
+                {
+                    val (id, node) = x
+                    log.error (s"$id missing ConnectivityNode $node")
+                }
+            )
         }
 
         // construct the initial graph from the edges
@@ -512,7 +528,7 @@ case class CIMNetworkTopologyProcessor (spark: SparkSession) extends CIMRDD
         island.bitfields = Array (0)
 
         (
-            nodes.head._1._1.island,
+            nodes.headOption.fold (0L)(x => x._1._1.island),
             island
         )
     }
@@ -712,8 +728,8 @@ case class CIMNetworkTopologyProcessor (spark: SparkSession) extends CIMRDD
         val ret: Graph[CIMVertexData, CIMEdgeData] = Graph.apply (v, graph.edges, CIMVertexData (), options.storage, options.storage)
 
         // persist the RDD to avoid recomputation
-        ret.vertices.persist (options.storage)
-        ret.edges.persist (options.storage)
+        { val _ = ret.vertices.persist (options.storage) }
+        { val _ = ret.edges.persist (options.storage) }
 
         ret
     }
@@ -775,14 +791,26 @@ case class CIMNetworkTopologyProcessor (spark: SparkSession) extends CIMRDD
             put (new_ti)
 
             val nodes_with_islands = graph.vertices.values.keyBy (_.island).join (islands).values
-            val nodes = nodes_with_islands.groupBy (_._1.node).map (x => (x._1, x._2.head._1, Some (x._2.head._2))).map (to_nodes)
+            val nodes = nodes_with_islands.groupBy (_._1.node)
+                // keep the head of the Iterable
+                // .map (x => (x._1, x._2.head))
+                .flatMapValues  (_.toList match { case head :: _ => Some (head) case _ => None })
+                .map (x => (x._1, x._2._1, Some (x._2._2))).map (to_nodes)
             if (options.debug && log.isDebugEnabled)
                 log.debug (s"${nodes.count} nodes")
+
+            // unpersist the graph nodes and edges
+            { val _ = graph.vertices.unpersist (false) }
+            { val _ = graph.edges.unpersist (false) }
             (nodes, new_ti)
         }
         else
         {
-            val nodes = graph.vertices.values.groupBy (_.node).map (x => (x._1, x._2.head, None)).map (to_nodes)
+            val nodes = graph.vertices.values.groupBy (_.node)
+                // keep the head of the Iterable
+                // .map (x => (x._1, x._2.head))
+                .flatMapValues  (_.toList match { case head :: _ => Some (head) case _ => None })
+                .map (x => (x._1, x._2, None)).map (to_nodes)
             if (options.debug && log.isDebugEnabled)
                 log.debug (s"${nodes.count} nodes")
             (nodes, spark.sparkContext.emptyRDD[TopologicalIsland])
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMNormalize.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMNormalize.scala
index 3b2629b20..ea1e3bdb4 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMNormalize.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMNormalize.scala
@@ -24,6 +24,7 @@ with
     Serializable
 {
     implicit val session: SparkSession = spark
+    implicit val level: StorageLevel = storage // for put()
     implicit val log: Logger = LoggerFactory.getLogger (getClass)
 
     /**
@@ -196,10 +197,7 @@ with
         val new_elements: RDD[Element] = cleaned.subtractByKey (fixed2).union (fixed2).values
 
         // swap the old Elements RDD for the new one
-        old_elements.name = "denormalized_Elements"
-        new_elements.name = "Elements"
-        new_elements.persist (storage)
-        if (spark.sparkContext.getCheckpointDir.isDefined) new_elements.checkpoint ()
+        put (new_elements, "Elements")
 
         new_elements
     }
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMRDD.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMRDD.scala
index d0669b12c..e0f058227 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMRDD.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMRDD.scala
@@ -154,15 +154,16 @@ trait CIMRDD
      * @return The named, viewed and possibly checkpointed original RDD.
      * @tparam T The type of RDD.
      */
-    def put[T <: Product : ClassTag : TypeTag](rdd: RDD[T], name: String)(implicit spark: SparkSession, storage: StorageLevel): RDD[T] =
+    def put[T <: Product : ClassTag : TypeTag](rdd: RDD[T], name: String)(implicit spark: SparkSession, storage: StorageLevel): Unit =
     {
-        spark.sparkContext.getPersistentRDDs.find (_._2.name == name) match
-        {
-            case Some ((_: Int, old: RDD[_])) =>
+        spark.sparkContext.getPersistentRDDs.find (_._2.name == name).foreach (
+            x =>
+            {
+                val (_, old) = x
                 old.setName (null).unpersist (true)
-            case Some (_) | None =>
-        }
-        rdd.setName (name).persist (storage)
+            }
+        )
+        val _ = rdd.setName (name).persist (storage)
         if (spark.sparkContext.getCheckpointDir.isDefined) rdd.checkpoint ()
         val tag: universe.TypeTag[T] = typeTag[T]
         val runtime_class: Class[_] = classTag[T].runtimeClass
@@ -174,7 +175,6 @@ trait CIMRDD
         }
         else
             spark.createDataFrame (rdd).createOrReplaceTempView (name)
-        rdd
     }
 
     /**
@@ -236,7 +236,7 @@ trait CIMRDD
      * @param storage The storage level for persistence.
      * @tparam T The type of RDD.
      */
-    def put[T <: Product : ClassTag : TypeTag](rdd: RDD[T])(implicit spark: SparkSession, storage: StorageLevel): RDD[T] = put (rdd, nameOf[T])
+    def put[T <: Product : ClassTag : TypeTag](rdd: RDD[T])(implicit spark: SparkSession, storage: StorageLevel): Unit = put (rdd, nameOf[T])
 
     /**
      * Get a typed DataSet for the given class.
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMRelation.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMRelation.scala
index d80422e82..72b4806d7 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMRelation.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMRelation.scala
@@ -171,9 +171,10 @@ class CIMRelation (
         var ret: RDD[Row] = null
 
         // remove any existing RDD created by this relation
-        spark.sparkContext.getPersistentRDDs.find (_._2.name == "Elements") match
-        {
-            case Some ((_: Int, old: RDD[_])) =>
+        spark.sparkContext.getPersistentRDDs.find (_._2.name == "Elements").foreach (
+            x =>
+            {
+                val (_, old) = x
                 // aggregate the set of subclass names
                 val names = old.asInstanceOf[RDD[Element]]
                     .aggregate (Set[String]()) (
@@ -190,8 +191,8 @@ class CIMRelation (
                     }
                 // remove the Element rdd
                 old.setName (null).unpersist (true)
-            case Some (_) | None =>
-        }
+            }
+        )
 
         if (_Cache != "")
         {
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/CIMSubsetter.scala b/CIMReader/src/main/scala/ch/ninecode/cim/CIMSubsetter.scala
index 351c439a6..e90fad9ba 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/CIMSubsetter.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/CIMSubsetter.scala
@@ -66,7 +66,7 @@ class CIMSubsetter[A <: Product : ClassTag : TypeTag] () extends Serializable
     def save (context: SQLContext, rdd: rddtype, storage: StorageLevel): Unit =
     {
         rdd.name = cls
-        rdd.persist (storage)
+        val _ = rdd.persist (storage)
         if (context.sparkSession.sparkContext.getCheckpointDir.isDefined) rdd.checkpoint ()
         val df = context.sparkSession.createDataFrame (rdd)(tag)
         val altered_schema = modify_schema (runtime_class, df.schema)
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/Context.scala b/CIMReader/src/main/scala/ch/ninecode/cim/Context.scala
index 13e6c20e3..39e98332a 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/Context.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/Context.scala
@@ -55,7 +55,9 @@ class Context (var xml: String, val start: Long, var end: Long, var first_byte:
     {
         val matcher = lines.matcher (string)
         while (matcher.find ())
-            n += (matcher.start () + offset)
+        {
+            val _ = n += (matcher.start () + offset)
+        }
         n
     }
 
@@ -66,6 +68,7 @@ class Context (var xml: String, val start: Long, var end: Long, var first_byte:
      * @param offset the character position in the stream
      * @return the line number (1 + how many newlines precede the offset)
      */
+    @SuppressWarnings (Array ("org.wartremover.warts.Return"))
     def line_number (offset: Long = end): Int =
     {
         var min = 0
@@ -106,7 +109,9 @@ class Context (var xml: String, val start: Long, var end: Long, var first_byte:
             {
                 ret &&= subxml.charAt (index).isWhitespace
                 if (!ret && errors.size < MAXERRORS)
-                    errors += """Unknown content "%s" at line %d""".format (subxml.substring (index, pair._1).trim (), line_number ())
+                {
+                    val _ = errors += """Unknown content "%s" at line %d""".format (subxml.substring (index, pair._1).trim (), line_number ())
+                }
                 index += 1
             }
             index = pair._2
@@ -115,7 +120,9 @@ class Context (var xml: String, val start: Long, var end: Long, var first_byte:
         {
             ret &&= subxml.charAt (index).isWhitespace
             if (!ret && errors.size < MAXERRORS)
-                errors += """Unknown content "%s" at line %d""".format (subxml.substring (index, subxml.length ()).trim (), line_number ())
+            {
+                val _ = errors += """Unknown content "%s" at line %d""".format (subxml.substring (index, subxml.length ()).trim (), line_number ())
+            }
             index += 1
         }
 
diff --git a/CIMReader/src/main/scala/ch/ninecode/cim/DefaultSource.scala b/CIMReader/src/main/scala/ch/ninecode/cim/DefaultSource.scala
index 9b21386ec..d5f68233a 100644
--- a/CIMReader/src/main/scala/ch/ninecode/cim/DefaultSource.scala
+++ b/CIMReader/src/main/scala/ch/ninecode/cim/DefaultSource.scala
@@ -33,14 +33,19 @@ extends
                 val globPath = SparkHadoopUtil.get.globPathIfNecessary (qualified)
                 if (globPath.isEmpty)
                     throw new java.io.FileNotFoundException (s"Path does not exist: $qualified")
-                if (!fs.exists(globPath.head))
-                    throw new java.io.FileNotFoundException (s"Path does not exist: ${globPath.head}")
+                globPath.foreach (
+                    p =>
+                    {
+                        if (!fs.exists (p))
+                            throw new java.io.FileNotFoundException (s"Path does not exist: $p")
+                    }
+                )
                 globPath
         }
         val fileCatalog = new InMemoryFileIndex (session, globbedPaths, parameters, None)
         val partitionSchema = fileCatalog.partitionSpec().partitionColumns
         val format = new CIMFileFormat ()
-        val dataSchema = format.inferSchema (session, parameters, fileCatalog.allFiles ()).get
+        val dataSchema = format.inferSchema (session, parameters, fileCatalog.allFiles ()).orNull
         new CIMRelation (fileCatalog, partitionSchema, dataSchema, format, parameters) (session)
     }
 }
diff --git a/CIMTool/src/main/scala/ch/ninecode/cim/tool/JavaDoc.scala b/CIMTool/src/main/scala/ch/ninecode/cim/tool/JavaDoc.scala
index ba099fa96..f43c4fcee 100644
--- a/CIMTool/src/main/scala/ch/ninecode/cim/tool/JavaDoc.scala
+++ b/CIMTool/src/main/scala/ch/ninecode/cim/tool/JavaDoc.scala
@@ -68,6 +68,8 @@ case class JavaDoc (
         strings.flatten
     }
 
+    def asterisk (s: String): String = if ("" == s) " *" else s" * $s"
+
     def contents: String =
     {
         val text: List[String] = if ((null != note) && (note != ""))
@@ -83,7 +85,7 @@ case class JavaDoc (
         }
         else
             List ()
-        (text :: groupStuff :: Nil).flatten .map (l => if ("" == l) " *" else s" * $l").mkString ("\n")
+        (text :: groupStuff :: Nil).flatten.map (asterisk).mkString ("\n")
     }
 
     def asText: String =