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The Scope of Step Names

From: Alex Milowski <alex@milowski.org>
Date: Mon, 02 Oct 2006 08:59:09 -0700
Message-ID: <4521374D.3050801@milowski.org>
To: public-xml-processing-model-wg <public-xml-processing-model-wg@w3.org>

In section 4.1.2, we have:

"The scope of component names is the flow graph of their container and 
the flow graphs of the constructs therein, recursively."

I think should have been 'step names'.  component names are global
as they represent a type of component that can be used in a step.

If you then trace down the definition of a flow graph, things become
very unclear.

Per last week's discussion, I think we need to delete the term flow
graph (and section 2.4) from the specification and just define the scope
of step names explicitly.

I think we have the following rules to consider:

1. Step must be able to refer to other steps that are
    siblings (preceding and following) otherwise you
    can't connected steps at all.

2. Steps must be able to refer to their step container
    because otherwise you can't bind to the input of
    the container (e.g. the input of the pipeline).

3. Steps should be able to refer to ancestors so that
    you can refer to ancestor inputs (e.g. a descendant
    may want to refer to the pipeline input).

4. Steps should be able to refer to siblings of

5. Steps should not be able to refer to any descendant steps
    of ancestors or siblings of ancestors that are
    step containers.  That is, you can't point inside a
    step container that isn't your ancestor.

Of these, (4) is probably the most "controversial".  Here is
a simple example coming from a refinement of an actual

<p:pipeline name="example">
   <p:declare-input port="pipe-input"/>
   <p:declare-input port="metadata"/>
   <p:declare-output port="pipe-output" source="main!output"/>

   <p:step name="prep-metadata" type="p:xslt">
       <p:input port="document" step="example" port="pipe-input"/>
       <p:input port="transform" href="prep-metadata.xsl"/>

   <p:viewport name="main">
     <p:declare-input port="part"
                      step="example" source="pipe-input"
     <p:declare-output port="output"
                       step="transform" source="result"/>
     <p:step name="insert" type="p:insert">
        <p:input port="document"
                 step="main" port="part"/>
        <p:input port="insertion"
                 step="prep-metadata" port="result"/>
     <p:step name="transform" type="p:xslt">
        <p:input port="document"
                 step="insert" port="result"/>
        <p:input port="transform" href="part.xsl"/>


In the above example, the step 'insert' refers to the sibling
step 'prep-metadata' of its ancestor 'main'.

--Alex Milowski
Received on Monday, 2 October 2006 15:59:23 UTC

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