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Re: Constant Inputs during Iteration

From: Erik Bruchez <ebruchez@orbeon.com>
Date: Mon, 02 Oct 2006 18:52:05 +0200
Message-ID: <452143B5.4020401@orbeon.com>
CC: public-xml-processing-model-wg <public-xml-processing-model-wg@w3.org>

Alex Milowski wrote:
 >
 > For both the 'viewport' and 'foreach' step containers, I think we
 > need a simple statement in the document that says that inputs
 > consumed by steps that aren't the subject of the iteration are
 > consider "constant" during the iteration.  Contained steps should
 > receive the same document for each iteration.

Agreed.

 > This all means that static resources (e.g. those pointed to with
 > an 'href') can't change during pipeline execution and be
 > considered as part of the computation.

Consider an iteration that:

o Stores a document into eXist as a step of the iteration

o Retrieves the updated version from eXist using the eXist REST API
   during the next iteration, with an HTTP URI like:

   http://example.org/exist/rest/db/latest.xml

In this case, the document retrieved with that HTTP URI would need to
be up to date during each iteration. In other words, while the URI is
static, the document is not static, and I think it would be wrong in
this use case to require that it be static. And if you want it to be
constant for the iteration, you have a simple workaround: you can
retrieve the resource outside p:for-each!

Also, requiring all static URIs to be constant requires the
implementation to use a sort of cache, even for "file:" URIs. I am not
sure that this is necessary.

-Erik

-- 
Orbeon - XForms Everywhere:
http://www.orbeon.com/blog/
Received on Monday, 2 October 2006 16:52:21 GMT

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