Clarify that all input parameters must be null if not assigned. Clarify that

`default` applies when the paramater value is `null`.

Author: Peter Amstutz

v1.0/Process.yml

@@ -567,8 +567,9 @@ $graph:
         _id: cwl:default
         noLinkCheck: true
       doc: |
-        The default value for this parameter if not provided in the input
-        object.
+        The default value to use for this parameter if the parameter is missing
+        from the input object, or if the value of the parameter in the input
+        object is `null`.
 
     - name: type
       type:
@@ -648,6 +649,13 @@ $graph:
         values.  Input parameters include a schema for each parameter which is
         used to validate the input object.  It may also be used to build a user
         interface for constructing the input object.
+
+        When accepting an input object, all input parameters must have a value.
+        If an input parameter is missing from the input object, it must be
+        assigned a value of `null` (or the value of `default` for that
+        parameter, if provided) for the purposes of validation and evaluation
+        of expressions.
+
     - name: outputs
       type:
         type: array

v1.0/Workflow.yml

@@ -260,8 +260,8 @@ $graph:
     - name: default
       type: ["null", Any]
       doc: |
-        The default value for this parameter if there is no `source`
-        field.
+        The default value for this parameter to use if either there is no
+        `source` field, or the value produced by the `source` is `null`.
       jsonldPredicate:
         _id: "cwl:default"
         noLinkCheck: true

v1.1.0-dev1/Process.yml

@@ -568,8 +568,9 @@ $graph:
         _id: cwl:default
         noLinkCheck: true
       doc: |
-        The default value for this parameter if not provided in the input
-        object.
+        The default value to use for this parameter if the parameter is missing
+        from the input object, or if the value of the parameter in the input
+        object is `null`.
 
 - name: RegularInputParameter
   type: record
@@ -653,6 +654,13 @@ $graph:
         values.  Input parameters include a schema for each parameter which is
         used to validate the input object.  It may also be used to build a user
         interface for constructing the input object.
+
+        When accepting an input object, all input parameters must have a value.
+        If an input parameter is missing from the input object, it must be
+        assigned a value of `null` (or the value of `default` for that
+        parameter, if provided) for the purposes of validation and evaluation
+        of expressions.
+
     - name: outputs
       type:
         type: array

v1.1.0-dev1/Workflow.yml

@@ -266,8 +266,8 @@ $graph:
     - name: default
       type: ["null", Any]
       doc: |
-        The default value for this parameter if there is no `source`
-        field.
+        The default value for this parameter to use if either there is no
+        `source` field, or the value produced by the `source` is `null`.
       jsonldPredicate:
         _id: "cwl:default"
         noLinkCheck: true