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RE: Implicit parameter input on p:pipeline

From: <Toman_Vojtech@emc.com>
Date: Mon, 28 Jan 2008 03:51:48 -0500
Message-ID: <6E216CCE0679B5489A61125D0EFEC78709880B36@CORPUSMX10A.corp.emc.com>
To: <public-xml-processing-model-comments@w3.org>

> / Toman_Vojtech@emc.com was heard to say:
> | Since the p:pipeline now always contains an implict "source" input 
> | port and an implicit "result" output port, I wonder if the 
> same cannot 
> | be done with the parameter inputs.
> |
> | Section 2.5 says:
> |
> | "Additionally, if a p:pipeline does not declare any parameter input
> Hmm, that should probably read "p:pipeline or p:declare-step" now.
> | ports, but contains a step which has a primary parameter 
> input port, 
> | then an implicit primary parameter input port (named 'parameters') 
> | will be added to the pipeline. (If the pipeline declares an 
> ordinary 
> | input named 'parameters', the implicit primary parameter input port 
> | will be named 'parameters1'. If that's not available, then 
> 'parameters2', etc.
> | until an available name is found.)"
> |
> | Cannot this be changed to something like:
> |
> | "All p:pipeline pipelines have an implicit primary parameter input 
> | port named 'parameters'. Any parameter input ports that the 
> p:pipeline 
> | declares explicitly are in addition to this port and may not be 
> | declared primary."
> It could, but I don't think it would be less confusing. I 
> don't expect explicit parameter ports to be needed very often 
> and probably almost never on a p:pipeline.

Are you sure? For me, one of the most typical pipelines looks as

<p:pipeline type="preview">
  <p:input port="stylesheet"/>
  <p:input port="parameters" kind="parameter"/>

    <p:input port="stylesheet">
      <p:pipe step="preview" port="stylesheet"/>
    <!-- the "parameters" port will be bound to the primary parameter
input port of the pipeline -->

The pipeline just takes a sequence of XML documents and applies a
(parametrized) XSLT stylesheet to them. The thing is that I can rewrite
it also as follows: 

<p:pipeline type="preview">
  <p:input port="stylesheet"/>

    <p:input port="stylesheet">
      <p:pipe step="preview" port="stylesheet"/>

In which case the primary parameter input port on the pipeline will be
manufactured automatically. This is fine, only that it makes developing
XProc-based application more difficult. In the latter case, the
application does not explictly know what parameter input port to use for
passing the XSLT parameters to the pipeline.


Vojtech Toman
Principal Software Engineer
EMC Corporation

Aert van Nesstraat 45
3012 CA Rotterdam
The Netherlands

Received on Monday, 28 January 2008 08:48:06 UTC

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