Clarify that default values apply prior to scattering and evaluating valueFrom.

Author: Peter Amstutz

v1.0/CommandLineTool.yml

@@ -203,11 +203,14 @@ $graph:
         If `valueFrom` is an expression, evaluate the expression to yield the
         actual value to use to build the command line and apply the binding
         rules above.  If the inputBinding is associated with an input
-        parameter, the value of `self` in the expression will be the value of the
-        input parameter.
+        parameter, the value of `self` in the expression will be the value of
+        the input parameter.  Input parameter defaults (as specified by the
+        `InputParameter.default` field) must be applied before evaluating the
+        expression.
 
         When a binding is part of the `CommandLineTool.arguments` field,
         the `valueFrom` field is required.
+
     - name: shellQuote
       type: boolean?
       doc: |

v1.0/Process.yml

@@ -569,7 +569,8 @@ $graph:
       doc: |
         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`.
+        object is `null`.  Default values are applied before evaluating expressions
+        (e.g. dependent `valueFrom` fields).
 
     - name: type
       type:

v1.0/Workflow.yml

@@ -261,7 +261,8 @@ $graph:
       type: ["null", Any]
       doc: |
         The default value for this parameter to use if either there is no
-        `source` field, or the value produced by the `source` is `null`.
+        `source` field, or the value produced by the `source` is `null`.  The
+        default must be applied prior to scattering or evaluating `valueFrom`.
       jsonldPredicate:
         _id: "cwl:default"
         noLinkCheck: true
@@ -287,10 +288,10 @@ $graph:
 
         The value of `inputs` in the parameter reference or expression must be
         the input object to the workflow step after assigning the `source`
-        values and then scattering.  The order of evaluating `valueFrom` among
-        step input parameters is undefined and the result of evaluating
-        `valueFrom` on a parameter must not be visible to evaluation of
-        `valueFrom` on other parameters.
+        values, applying `default`, and then scattering.  The order of
+        evaluating `valueFrom` among step input parameters is undefined and the
+        result of evaluating `valueFrom` on a parameter must not be visible to
+        evaluation of `valueFrom` on other parameters.
 
 
 - type: record