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RE: An XPath function is needed for accessing the filter's paren t context

From: Kay, Michael <Michael.Kay@softwareag.com>
Date: Thu, 20 Dec 2001 16:35:39 +0100
Message-ID: <DFF2AC9E3583D511A21F0008C7E6210622B895@softwareag.com>
To: "'Stanislav Vitebskiy'" <svitebskiy@pivotal.com>, w3c-xsl-wg@w3.org, xsl-editors@w3.org
Thanks for the suggestion. We know there's a gap here: if we can ask for
just a tiny bit of patience until the XPath 2.0 working draft comes out, I
hope you'll like the way the problem has been tackled.

Mike Kay

> -----Original Message-----
> From: Stanislav Vitebskiy [mailto:svitebskiy@pivotal.com]
> Sent: 19 December 2001 22:04
> To: w3c-xsl-wg@w3.org; xsl-editors@w3.org
> Subject: An XPath function is needed for accessing the filter's parent
> context
> 
> 
> Here is a simple problem: select all the <customer> elements
> that have <employee> sibling with the same 'name' attribute.
> The solution is pretty obvious:
> 	customer[@name = ../employee/@name]
> 
> Lets now complicate the task a little. Let the name consist of
> two parts, 'first-name' and 'last-name'.
> Little complication - big problem: the technique shown above
> will no longer work; there is no way to compare more than one
> attribute of different elements, and there is no workaround in
> the current version of XPath.
> 
> My suggestion (it could have been offered before, but I failed
> to locate any mention of it) is to add a function that returns
> the context against which the filter expression is being
> evaluated. The example above can be rewritten like this:
> 	customer[../employee[@name = parent-context()/@name]]
> In this case, parent-context() returns the <customer> element
> against which <employee> siblings are being checked.
> 
> The advantage of this approach is that it can easily be extended
> to comparing multiple attributes/elements/etc. The problem
> described in the second paragraph (that XPath 1.0 cannot handle)
> can now be solved by this expression:
> 	customer[../employee[
> 		@first-name = parent-context()/@first-name
> 		and
> 		@last-name = parent-context()/@last-name]]
> 
> 
> PS., If you think that there is a better way to do it, or that
> the current XPath can somehow tackle the problem described
> here, please let us all know.
> 
Received on Thursday, 20 December 2001 10:35:45 GMT

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