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Explicit vs. implicit parameter bindings

From: Norman Walsh <ndw@nwalsh.com>
Date: Sun, 12 Oct 2008 11:48:38 -0400
To: public-xml-processing-model-wg@w3.org
Message-ID: <m2bpxp3jc9.fsf@nwalsh.com>
Consider this pipeline:

<p:declare-step xmlns:p="http://www.w3.org/ns/xproc"
		xmlns:px="http://example.org/ns/pipelines"
		xmlns:c="http://www.w3.org/ns/xproc-step"
		name="main">
<p:input port="parameters" kind="parameter">
  <p:inline>
    <c:param-set>
      <c:param name="foo" value="1"/>
    </c:param-set>
  </p:inline>
</p:input>
<p:input port="source"/>
<p:output port="result">
  <p:pipe step="params" port="result"/>
</p:output>

<p:parameters name="params">
  <p:input port="parameters">
    <p:pipe step="main" port="parameters"/>
  </p:input>
  <p:with-param name="foo" select="'bar'"/>
</p:parameters>

</p:declare-step>

The output of this pipeline is a c:param-set element with "foo='bar'"
because the with-param occurs after the parameter input port.

If we reverse the order of the elements in the p:parameters step:

<p:parameters name="params">
  <p:with-param name="foo" select="'bar'"/>
  <p:input port="parameters">
    <p:pipe step="main" port="parameters"/>
  </p:input>
</p:parameters>

Then the output of this pipeline is a c:param-set element with "foo='1'"
because the with-param occurs before the parameter input port.

We all agree so far, right?

So what's the output if we specify the p:parameters step this way?

<p:parameters name="params">
  <p:with-param name="foo" select="'bar'"/>
</p:parameters>

In other words, what is the relative order of the implicit bindings?

I'm inclined to say they come last, that they come after the things
that you specify explicitly. But I think that by the principle of
least surprise, the value specified by the lone with-param should be
respected.

Thoughts?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | I'm NOT in denial!
http://nwalsh.com/            | 

Received on Sunday, 12 October 2008 15:49:22 GMT

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