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Re: p:pipeline

From: Alessandro Vernet <avernet@orbeon.com>
Date: Wed, 2 Aug 2006 18:04:19 -0700
Message-ID: <4828ceec0608021804gf5e5a8etb222bf817d850f81@mail.gmail.com>
To: public-xml-processing-model-wg <public-xml-processing-model-wg@w3.org>


On 7/27/06, Jeni Tennison <jeni@jenitennison.com> wrote:
> 1. It means pipeline definitions can be dynamically generated by other
> pipelines, which means that pipelines can't be compiled.

Yes: it means that pipeline definitions can be dynamically generated.
But no, it does not mean that pipelines can't be compiled. Pipelines
can always be compiled. The result from the compilation may of may not
be reusable, depending if the pipeline has changed. For pipelines
stored in separate files, a compiling engine needs to check if the
file containing the pipeline has changed, whatever syntax we choose.

If the pipeline is truly dynamically generated, say with XSLT, then
the engine can either consider that it is different pipeline every
time, or be a more "clever" and try to figure out if it has really
changed. (We have implemented the latter in XPL.)

> 2. Calling a pipeline becomes very difficult. The 'call-pipeline'
> component needs to have a 'pipeline' input, an 'inputs' input, and an
> 'outputs' output. All the inputs for the pipeline have to be defined
> somehow within the 'inputs' input, which requires another complex
> syntax. This is analogous to the problem we have with passing XSLT
> parameters to an XSLT component.

Calling a pipeline would not be more difficult than calling a
stylesheet. If we have a construct we find good enough to run a
stylesheet, why wouldn't it be good enough to run a pipeline? If
calling pipelines happened much more frequently than calling
stylesheets, one could argue that there could be some value in having
a shortcut for that specific case. But in my experience, this is not
the case, and calls to stylesheets in general happen more frequently
that calls to pipelines.

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Received on Thursday, 3 August 2006 01:04:29 UTC

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