diff --git a/passes/src/main/scala/com/reactific/riddl/passes/Pass.scala b/passes/src/main/scala/com/reactific/riddl/passes/Pass.scala
index 5f3095c13..41f4a9624 100644
--- a/passes/src/main/scala/com/reactific/riddl/passes/Pass.scala
+++ b/passes/src/main/scala/com/reactific/riddl/passes/Pass.scala
@@ -19,10 +19,17 @@ import scala.annotation.unused
 import scala.collection.mutable
 import scala.util.control.NonFatal
 
+/**
+ * Information a pass must provide, basically its name
+ */
 trait PassInfo {
   def name: String
 }
 
+/**
+ * Information that a Pass must produce, currently just any messages it generated.
+ * Passes should derive their own concrete PassOutput classes from this trait
+ */
 trait PassOutput {
   def messages: Messages.Messages
 }
@@ -31,6 +38,14 @@ object PassOutput {
   def empty: PassOutput = new PassOutput { val messages: Messages.Messages = Messages.empty }
 }
 
+/**
+ * The input to a Pass in order to do its work. This consists of just the parsed model
+ * and the common options. Passes cannot extend this.
+ * @param root
+ *   The result of the parsing run, consisting of the RootContainer from which all AST content can be reached
+ * @param commonOptions
+ *   THe common options that should be used to run the pass
+ */
 case class PassInput(
   root: RootContainer,
   commonOptions: CommonOptions = CommonOptions.empty
@@ -39,6 +54,11 @@ object PassInput {
   val empty: PassInput = PassInput(RootContainer.empty)
 }
 
+/**
+ * The output from running a set of Passes. This collects the PassOutput
+ * instances from each Pass run and provides utility messages for getting
+ * that information.
+ */
 case class PassesOutput() {
 
   private val outputs: mutable.HashMap[String, PassOutput] = mutable.HashMap.empty
@@ -65,6 +85,18 @@ case class PassesOutput() {
     outputs.toMap.filterNot(Pass.standardPassNames.contains(_))
 }
 
+/**
+ * The result of running a set of passes. This provides the input and ouputs
+ * of the run as well as any additional messages (likely from an exception)
+ * This provides convenience methods for accessing the various output content
+ *
+ * @param input
+ * The input provided to the run of the passes
+ * @param outputs
+ * The PassesOutput collected from teh run of the Passes
+ * @param additionalMessages
+ * Any additional messages, likely from an exception or other unusual circumstance.
+ */
 case class PassesResult(
   input: PassInput = PassInput.empty, outputs: PassesOutput = PassesOutput(), additionalMessages: Messages = Messages
   .empty
@@ -74,11 +106,11 @@ case class PassesResult(
   lazy val messages: Messages = {
     outputs.getAllMessages ++ additionalMessages
   }
-  lazy val symbols: SymbolsOutput = 
+  lazy val symbols: SymbolsOutput =
     outputs.outputOf[SymbolsOutput](SymbolsPass.name).getOrElse(SymbolsOutput())
-  lazy val resolution: ResolutionOutput = 
+  lazy val resolution: ResolutionOutput =
     outputs.outputOf[ResolutionOutput](ResolutionPass.name).getOrElse(ResolutionOutput())
-  lazy val validation: ValidationOutput = 
+  lazy val validation: ValidationOutput =
     outputs.outputOf[ValidationOutput](ValidationPass.name).getOrElse(ValidationOutput())
 
   def refMap: ReferenceMap = resolution.refMap
@@ -97,10 +129,18 @@ object PassesResult {
   val empty: PassesResult = PassesResult()
 }
 
-/** Abstract Pass definition */
+/**
+ * Abstract Pass definition.
+ * @param in
+ * The input to the pass. This provides the data over which the pass is executed
+ * @param out
+ * The output from previous runs of OTHER passes, which is a form of input to
+ * the pass, perhaps.
+ */
 abstract class Pass(@unused val in: PassInput, val out: PassesOutput) {
 
-  /** THe name of the pass for inclusion in messages it produces
+  /** THe name of the pass for inclusion in messages it produces. This must
+    * be implemented by the subclass
     * @return
     *   A string value giving the name of this pass
     */
@@ -115,11 +155,29 @@ abstract class Pass(@unused val in: PassInput, val out: PassesOutput) {
     require(out.hasPassOutput(passInfo.name), s"Required pass '${passInfo.name}' was not run prior to $name'")
   }
 
+  /** The main implementation of the Pass. The AST is walked in a depth first manner calling this
+   * function for each definition it encounters.
+   *
+   * @param definition
+   *   The definition to be processed
+   * @param parents
+   *   The stack of definitions that are the parents of [[definition]]. This stack goes from immediate parent towards
+   *   the root. The root is deepest in the stack.
+   */
   protected def process(
     definition: Definition,
     parents: mutable.Stack[Definition]
   ): Unit
 
+  /** A signal that the processing is complete and no more calls to [[process]] will be made. This also gives the
+   * Pass subclass a chance to do post-processing as some computations can only be done after collecting data from
+   * the entire AST
+   *
+   * @param root
+   *   The [[in]].root field just as a convenience
+   * @return
+   *   Unit
+   */
   def postProcess(root: RootContainer): Unit
 
   /** Generate the output of this Pass. This will only be called after all the calls to process have completed.
@@ -144,20 +202,21 @@ abstract class Pass(@unused val in: PassInput, val out: PassesOutput) {
   protected val messages: Messages.Accumulator = Messages.Accumulator(in.commonOptions)
 }
 
-/** A pass base class that allows the node processing to be done in a depth first hierarchical order by calling:
+/** A Pass base class that allows the processing to be done based on containers, and calling these methods:
   *   - openContainer at the start of container's processing
-  *   - processLeaf for any leaf node
-  *   - closeContainer after all the container's contents have been processed This kind of Pass allows the processing to
-  *     follow the AST hierarchy so that container nodes can run before all their content (openContainer) and also after
-  *     all its content (closeContainer). This is necessary for passes that must maintain the hierarchical structure of
-  *     the AST model in their processing
+  *   - processLeaf for any leaf nodes within the container
+  *   - closeContainer after all the container's contents have been processed
+  *
+  * This kind of Pass allows the processing to follow the AST hierarchy so that container nodes can run before all
+  * their content (openContainer) and also after all its content (closeContainer). This is necessary for passes that
+  * must maintain the hierarchical structure of the AST model in their processing.
   *
   * @param input
   *   The PassInput to process
   */
 abstract class HierarchyPass(input: PassInput, outputs: PassesOutput) extends Pass(input, outputs) {
 
-  // not required in this kind of pass, final override it
+  // not required in this kind of pass, final override it as a result
   override final def process(definition: AST.Definition, parents: mutable.Stack[AST.Definition]): Unit = ()
 
   // Instead traverse will use these three methods:
@@ -167,6 +226,7 @@ abstract class HierarchyPass(input: PassInput, outputs: PassesOutput) extends Pa
 
   protected def closeContainer(definition: Definition, parents: Seq[Definition]): Unit
 
+  // Redefine traverse to make the three calls
   override protected def traverse(definition: Definition, parents: mutable.Stack[Definition]): Unit = {
     definition match {
       case leaf: LeafDefinition =>
@@ -183,28 +243,46 @@ abstract class HierarchyPass(input: PassInput, outputs: PassesOutput) extends Pa
   }
 }
 
+/** An abstract PassOutput for use with passes that derive from CollectingPass.
+ * This just provides a standard field name for the data that is collected,
+ * being `collected`.
+ *
+ * @param messages
+ *   The required messages field from the PassOutput trait
+ * @param collected
+ *   The data that was collected from the CollectingPass's run
+ * @tparam T
+ *   The element type of the collected data
+ */
 abstract class CollectingPassOutput[T](
   messages: Messages = Messages.empty,
   collected: Seq[T] = Seq.empty[T]
 ) extends PassOutput
 
-/** A pass base class that allows the node processing to be done in a depth first hierarchical order by calling:
-  *   - openContainer at the start of container's processing
-  *   - processLeaf for any leaf node
-  *   - closeContainer after all the container's contents have been processed This kind of Pass allows the processing to
-  *     follow the AST hierarchy so that container nodes can run before all their content (openContainer) and also after
-  *     all its content (closeContainer). This is necessary for passes that must maintain the hierarchical structure of
-  *     the AST model in their processing
+/** A Pass subclass that processes the AST exactly the same as the depth first search that
+  * the Pass class uses. The only difference is that
   *
   * @param input
   *   The PassInput to process
+  * @param outputs
+  *  The outputs from previous pass runs in case they are needed as input to this CollectingPass
+  * @tparam F
+  *  The element type of the collected values
   */
 abstract class CollectingPass[F](input: PassInput, outputs: PassesOutput) extends Pass(input, outputs) {
 
   // not required in this kind of pass, final override it
   override final def process(definition: AST.Definition, parents: mutable.Stack[AST.Definition]): Unit = ()
 
-  // Instead traverse will use this fold method
+  /** The processing method called at each node, similar to [[Pass.process]] but modified to return an
+   *
+   * @param definition
+   *   The definition from which an [[F]] value is collected.
+   * @param parents
+   *   The parents of the definition
+   * @return
+   *   One of the collected values, an [[F]]
+   */
   protected def collect(definition: Definition, parents: mutable.Stack[AST.Definition]): F
 
   @SuppressWarnings(Array("org.wartremover.warts.Var"))
@@ -222,15 +300,24 @@ abstract class CollectingPass[F](input: PassInput, outputs: PassesOutput) extend
 
 object Pass {
 
+  /** A function type that creates a Pass instance */
   type PassCreator = (PassInput, PassesOutput) => Pass
+
+  /** A sequence of PassCreator. This is used to run a set of passes */
   type PassesCreator = Seq[PassCreator]
 
+  /** A PassesCreator of the standard passes that should be run on every
+   * AST pass. These generate the symbol table, resolve path references, and
+   * validate the input. Only after these three have passed successfull should
+   * the model be considered processable by other passes
+   */
   val standardPasses: PassesCreator = Seq(
     { (input: PassInput, outputs: PassesOutput) => SymbolsPass(input, outputs) },
     { (input: PassInput, outputs: PassesOutput) => ResolutionPass(input, outputs) },
     { (input: PassInput, outputs: PassesOutput) => ValidationPass(input, outputs) }
   )
 
+  /** The name of the standard passes */
   val standardPassNames: Seq[String] = Seq(SymbolsPass.name, ResolutionPass.name, ValidationPass.name)
 
   /** Run a set of passes against some input to obtain a result
@@ -307,6 +394,7 @@ object Pass {
       val parents: mutable.Stack[Definition] = mutable.Stack.empty
       pass.traverse(in.root, parents)
       pass.postProcess(in.root)
+      pass.close()
       val output = pass.result
       outs.outputIs(pass.name, output)
       output