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Re: Usage of Asterisk in XPath expressions

Subject: Re: Usage of Asterisk in XPath expressions
From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Fri, 22 Mar 2019 16:51:10 -0000
Re:  Usage of Asterisk in XPath expressions
As Martin points out, this syntax is legal (as a multiplication operator) in
XPath 3.1, but not in XPath 2.0. This should explain why the behaviour has
changed from one Saxon version to another. In Saxon 9.7, XPath 3.1 syntax was
only available if explicitly requested, but in Saxon 9.8 it became the

Whether it succeeds or fails at execution time depends on the source document:
if there's no ancestor named foo and/or no attribute named a then it will
succeed and return an empty sequence, whose effective boolean value is false.

Specifying version="2.0" doesn't prevent an XSLT 3.0 processor accepting 3.0
(or 3.1) syntax; it provides a clue that you weren't intending to take
advantage of 3.0 syntax, but that's all.

Terse languages such as XPath (and regular expressions) do have the
disadvantage that when you get the syntax wrong, your expression often means
something unintended rather than being invalid.

Michael Kay

> On 22 Mar 2019, at 11:01, Philipp Nanz philipp.nanz@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello there,
> due to a typo, we missed the colon between the namespace prefix and the
wildcard in a XPath expression. To my surpise, this causes static errors in
some version of Saxon and runs flawlessly in others, although I would expect
this to be static error.
> Suppose this data:
> <foo:bar xmlns:foo="http://test/ns/foo" a="b">Yadda</foo:bar>
> Then suppose this stylesheet:
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>     xmlns:foo="http://test/ns/foo"
>     version="2.0">
>     <xsl:template match="foo:bar">
>         <xsl:if test="ancestor-or-self::foo*[@a]">
>             <xsl:copy>
>                 <xsl:value-of select="."/>
>             </xsl:copy>
>         </xsl:if>
>     </xsl:template>
> </xsl:stylesheet>
> As you can see the colon is missing after the namespace prefix foo. What
baffles me is that different versions of Saxon exhibit different behavious
here, and especially newer versions don't seem to treat this as a problem at
> * Saxon 9.6: Stops with something that looks like an internal error
> * Saxon 9.7: Says I need to enable XPath 3.1 to use this expression?!?
> * Saxon 9.8, 9.9: Don't run into an error at all
> That makes me wonder: Is this an error at all? or is there some wildcard
feature or something in XPath 3.1 that I cam't find in the docs?
> Thanks in advance for any insights!
> Kind regards,
> Philipp

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