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[Bug 24490] New: Rewriting expressions for streamability is mandatory but not clearly defined

From: <bugzilla@jessica.w3.org>
Date: Wed, 05 Feb 2014 00:50:05 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-24490-523@http.www.w3.org/Bugs/Public/>

            Bug ID: 24490
           Summary: Rewriting expressions for streamability is mandatory
                    but not clearly defined
           Product: XPath / XQuery / XSLT
           Version: Last Call drafts
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XSLT 3.0
          Assignee: mike@saxonica.com
          Reporter: abel.braaksma@xs4all.nl
        QA Contact: public-qt-comments@w3.org

In 19.1 we say the following:

"In order to make such expressions streamable, implementations must therefore
detect this situation in the construct tree and perform an appropriate rewrite
before continuing with the analysis. Specifically, any PathExpr E that is the
equivalent expression of some motionless pattern P is replaced by a call on a
streamable function that selects the same nodes as would have been selected by
E in the absence of streaming restrictions. This function call has a sweep of
consuming and a posture of crawling; its static type is that of the original
expression E. This makes it eligible to be used, for example, as the argument
of the count function."

We write "must" in this sentence, but I am not sure how we can enforce this for
every (non-streamable) expression E that has an equivalent expression that is a
motionless pattern P.

I think it is better to relax this requirement, for instance to allow
processors to rewrite expressions, or to warn about them and suggest
equivalents, but to not make this mandatory.

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Received on Wednesday, 5 February 2014 00:50:11 UTC

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