RE: [xsl] positional predicates in XPath vs XQL

["Michael Kay" <michael dot h dot kay at ntlworld dot com>]

No, The XPath query /section/para[1] retrieves the first para element of
every section. What made you think otherwise?

Mike Kay

> -----Original Message-----
> From: owner-xsl-list@lists.mulberrytech.com
> [mailto:owner-xsl-list@lists.mulberrytech.com]On Behalf Of Howard Katz
> Sent: 23 November 2001 23:36
> To: XSL-List@lists.mulberrytech.com
> Subject: [xsl] positional predicates in XPath vs XQL
>
>
> I'm implementing an engine that evaluates XPath. I'm
> currently working on
> the part of the engine that implements positional predicates. I've
> previously worked this out for location paths in XQL, but I think the
> semantics are different in the two languages and want to make sure I
> understand the differences.
>
> In XQL if you say (pretending for the moment that positions
> start from 1 as
> they do in XPath, rather than 0):
>
>      /section/para[ 1 ]
>
> and you have a tree that looks like this:
>
> 1  section
> 2       para
> 3       para
> 4  section
> 5       para
> 6  section
> 7       para
> 8       para
> 9       para
>
> you'll get back this nodeset:
>
> <2>, <5>, <7>
>
> You can paraphrase this XQL query as saying, "Give me back
> the 1st child
> node of each <section> element." Similarly, "/section/para[ 2
> ]" returns
> <3>, <8>, and if you say "/section/para[ 3 ]", you get back
> the single node,
> <9>.
>
> To my understanding, the same location path in XPath only
> returns a single
> node, <2>. Is my understanding correct?
>
> Howard
>
>
>
>
>
>
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