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[Bug 20639] XPath provides insufficient "glue" (modularity)

From: <bugzilla@jessica.w3.org>
Date: Fri, 11 Jan 2013 19:33:56 +0000
To: public-qt-comments@w3.org
Message-ID: <bug-20639-523-otH8GR7qB0@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=20639

Liam R E Quin <liam@w3.org> changed:

           What    |Removed                     |Added
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                 CC|                            |liam@w3.org

--- Comment #16 from Liam R E Quin <liam@w3.org> ---
Roger, as things stand there are very few stand-alone XPath 2 implementations.
Almost all XPath that's used outside XQuery or XSLT today is XPath 1.

Everything from Web browsers, PHP, C libraries, C++ bindings, Perl, Java,
Python, Scala, Scheme, and XML vocabularies like XForms, are primarily using
XPath 1.

This is for several reasons. The first is that there isn't a suitably-licensed
XPath 2 (or later) implementation written in portable C (not C++, C). And
no-one is getting very far in writing one because the language is too large and
XPath 1is almost good enough.  The second is that XPath 2 is large enough that
Web browsers and Web server plugins are nervous of the memory footprint.

If we do an XPath 3.1 I'm already thinking we should consider moving some core
features out and make them optional. XPath needs to be the obvious first choice
for pointing into XML-interchangeable trees, not a software engineering
platform.

If you want an extension to XPath that provides modules, it's called XQuery.

Sure, it's neat to be able to define functions in XPath, although I think we
were probably wrong to add it outside of XSLT and Query. Requiring XPath
engines to support closures and joins is probably a death sentence for the
language.

On the other foot, I think we are all pleased when someone likes one of our
specifications this much, and finds it cool and neat. Sometimes we forget that
perspective, because we are so close to it.  So I was pleased to see the
comment, even if I happen not to agree that it's a good direction for XPath.
But for sure we should discuss it in the XSLT and XQuery Working Groups.

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