Re: Restrictions on XPath expressions in <xsl:key>

Play the video

Subject: Re: Restrictions on XPath expressions in <xsl:key>
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 19 Dec 2007 16:59:47 -0500

At 2007-12-19 16:39 -0500, Nassar, Anthony wrote:

Does someone know a reason why this won't compile:

<xsl:key name="templates"
match="/onm:NetworkModel/onm:Graph/(onm:Nodes|onm:Links)/(onm:Link|onm:N
ode)/onm:Templates/onm:Template" use="@Name" />

Because match= attributes are restricted to be XPath patterns, not all XPath expressions.

...but this will:

<xsl:template match="onm:Graph">
    <xsl:copy>
        <xsl:if
test="(onm:Nodes/onm:Node|onm:Links/onm:Link)/onm:Attributes/onm:Attribu
te">

Because test= is not restricted to only being a pattern.

In other words, why can't an XPath expression in an <xsl:key> element
include parentheses and union operators?

Because patterns are restricted expressions that promote compile-time algorithms for detecting patterns of nodes in the source tree. Not all expressions are like this, so the XPath designers categorized a subset of all XPath expressions, called them patterns, and they are the only ones allowed in a match= attribute.

By the way, what is the order
of precedence between '/' and '|'? I'd understand '\' to have higher
precedence, in which case the latter expression above is actually wrong,
though it's been working for me.

A step separator "/" has higher precedence in the syntax than the expression separator "|", which is why the parentheses are needed to tell a processor that the step is made up of two separate expressions.

Note that in XPath 1.0 the expression separator and parentheses are only allowed in the first step of a multiple-step location path.

I'm using .NET 2.0, so let me know if this is a platform question, in
which case I'll post elsewhere.

It is an XSLT 2.0 question, not a platform-dependent question.

I hope this helps.

. . . . . . . . . . . . . Ken

--
Comprehensive in-depth XSLT2/XSL-FO1.1 classes: Austin TX,Jan-2008
World-wide corporate, govt. & user group XML, XSL and UBL training
RSS feeds:     publicly-available developer resources and training
G. Ken Holman                 mailto:gkholman@xxxxxxxxxxxxxxxxxxxx
Crane Softwrights Ltd.          http://www.CraneSoftwrights.com/s/
Box 266, Kars, Ontario CANADA K0A-2E0    +1(613)489-0999 (F:-0995)
Male Cancer Awareness Nov'07  http://www.CraneSoftwrights.com/s/bc
Legal business disclaimers:  http://www.CraneSoftwrights.com/legal

Current Thread
Restrictions on XPath expressions in <xsl:key> Nassar, Anthony - 19 Dec 2007 21:43:02 -0000 David Carlisle - 19 Dec 2007 21:49:29 -0000 Message not available G. Ken Holman - 19 Dec 2007 22:00:39 -0000 <= Michael Kay - 19 Dec 2007 22:15:40 -0000

<- Previous	Index	Next ->
Re: Restrictions on XPath exp, David Carlisle	Thread	RE: Restrictions on XPath exp, Michael Kay
Re: Restrictions on XPath exp, David Carlisle	Date	RE: Restrictions on XPath exp, Michael Kay
	Month

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Subscribe in XML format

RSS 2.0
Atom 0.3

XML Editor - Download a 15 Day Free Trial Now >

See What's New in Stylus Studio >

Buy Stylus Studio - XML Editor - Now >