W3C home > Mailing lists > Public > xproc-dev@w3.org > April 2009

Re: Where's the parallelize step?

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Mon, 20 Apr 2009 13:49:12 +0100
To: "Costello, Roger L." <costello@mitre.org>
Cc: "'xproc-dev@w3.org'" <xproc-dev@w3.org>
Message-ID: <f5b4owjh4mv.fsf@hildegard.inf.ed.ac.uk>
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Costello, Roger L. writes:

> I think there is a difference between:
>
>  - an XProc processor recognizing that some 
>    steps can be run in parallel
>
>    versus
>
>  - a user creating an XML workflow, declaring  
>    that "steps A, B, C can be run in parallel 
>    with steps D, E, F"
>
>
> The former is an XProc processor optimization activity. The latter
> is a user modeling activity.
>
> I think that it is important for a user to be able to explicitly
> state in an XProc document "These two workflow activities
> (subpipelines) may be run in parallel." (Whether an XProc processor
> executes the subpipelines in parallel or serially is an
> implementation issue.)

Hmm, I'm worried we still have a disconnect.

If I write the following pipeline:

  <p:declare-step name="top">
   <p:input port="i1" primary="false"/>
   <p:input port="i2" primary="false"/>

   <p:output port="o1" primary="false">
    <p:pipe step="sp1b" port="result"/>
   </p:output>

   <p:output port="o2" primary="false">
    <p:pipe step="sp2b" port="result"/>
   </p:output>

   <p:... name="sp1a">
    <p:input>
     <p:pipe step="top" port="i1"/>
    </p:input>
   </p:...>
    . . .
   <p:... name="sp1b">
    . . .
   </p:...>

   <p:... name="sp2a">
    <p:input>
     <p:pipe step="top" port="i2"/>
    </p:input>
   </p:...>
    . . .
   <p:... name="sp2b">
    . . .
   </p:...>

  </p:declare-step>

do you think there is something that _prevents_ the two sub-pipelines
- From running in parallel if you _don't_ say they can?  If so, I
believe that's a misreading of the spec.

It is of course open to you to add

 <p:documentation>Note that the implicit subpipe beginning with this step
         and ending with step sp1b may run in parallel with
         the implicit subpipe beginning with step sp2a.</p:documentation>

to sp1a, but we don't need a language change to make that possible.

How is what you have in mind different from this?

ht
- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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Received on Monday, 20 April 2009 12:49:51 GMT

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