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[Bug 27125] New: [XSLT30] Rules of override-extension-functions and xsl:override

From: <bugzilla@jessica.w3.org>
Date: Wed, 22 Oct 2014 14:11:51 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-27125-523@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=27125

            Bug ID: 27125
           Summary: [XSLT30] Rules of override-extension-functions and
                    xsl:override
           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

This is a bug report that covers the unresolved part of
https://lists.w3.org/Archives/Member/w3c-xsl-wg/2014Sep/0036.html and
https://lists.w3.org/Archives/Member/w3c-xsl-wg/2014Sep/0039.html (member only)
and related mail discussion.

Summary of that part:

The XSLT30 LCWD (Oct 2014) says that when you override an xsl:function and that
function has override-extension-functions="no", then the overriding function
must also specify override-extension-functions="no".

Use-case summary:

Package A:
<xsl:function name="exsl:random-sequence" 
    override-extension-functions="no">
    <!--
       custom implementation, but if exsl:random-sequence (EXSLT.org)
       is supported, then processor should use internal version
     -->
</xsl:function>

Package B:
<xsl:override>
    <xsl:function name="exsl:random-sequence" 
       override-extension-functions="yes">
       <!-- 
          User wants to make use of the new fn:random-sequence of XP31
          implementation using XPath 3.1 random sequence
        -->
    </xsl:function>
</xsl:override>

Result:
[ERR XTSE3070] It is a static error if the signature of an overriding component
is not compatible with the signature of the component that it is overriding.

Relevant spec part:

Definition of "compability":
https://www.w3.org/XML/Group/qtspecs/specifications/xslt-30/html/Overview-diff.html#dt-compatible
(member only), item 4 of the second bullet:

<quote>
If the overridden function specifies override-extension-functions="no" (or the
equivalent using the deprecated override attribute) then the overriding
function also specifies override-extension-functions="no" (or the equivalent).
</quote>

Proposed solution:

Remove this rule (not the error), because it limits users choosing to switch to
(new) internal XPath 3.1 or later, or XSLT 3.x or later functions as a
preference over internal implementations and as such, limits extensibility and
more importantly, inter-processor compatibility.

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Received on Wednesday, 22 October 2014 14:11:52 UTC

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