Merge pull request #40 from kaushik-work/master

Clarify ET can be run standalone

Author: mr-c

Workflow.yml

@@ -48,6 +48,7 @@ $graph:
 
       ## Changelog
 
+        * Clarify intent of ExpressionTool and clarify that they can be run standalone. 
         * Clarify how Requirements are inherited by step processes.
         * Clarify behavior around step inputs not consumed by the target
           run process.
@@ -177,7 +178,13 @@ $graph:
       specializeTo: ExpressionToolOutputParameter
   documentRoot: true
   doc: |
-    Execute an expression as a Workflow step.
+    An ExpressionTool is a type of Process object that can be run by itself
+    or as a Workflow step. It executes a pure Javascript expression that has
+    access to the same input parameters as a workflow. It is meant to be used
+    sparingly as a way to isolate complex Javascript expressions that need to
+    operate on input data and produce some result; perhaps just a
+    rearrangement of the inputs. No Docker software container is required
+    or allowed.
   fields:
     - name: class
       jsonldPredicate: