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RE: XQuery Puzzle

• From: "Michael Kay" <mike@s...>
• To: "'Fraser Goffin'" <goffinf@g...>,"'xml-dev'" <xml-dev@l...>
• Date: Thu, 17 Apr 2008 21:15:15 +0100

Path expressions in XQuery always behave like in XPath 2.0, except that in
XQuery some of the axes might not be supported.

The fact that this expression has multiple predicates is irrelevant to your
problem. The main path doesn't select anything, so the predicates are never
evaluated.

Michael Kay
http://www.saxonica.com/ 

> -----Original Message-----
> From: Fraser Goffin [mailto:goffinf@g...] 
> Sent: 17 April 2008 19:12
> To: xml-dev
> Subject: Re:  XQuery Puzzle
> 
> Is there any difference in the way that XPath 1.0 and 2.0 
> evaluate multiple predicates like this (there was a different 
> result between some of the XQuery processors used and it 
> wasn't clear whether these implemented XPath 1.0 or 2.0) ?
> 
> Fraser.
> 
> On 17/04/2008, Michael Kay <mike@s...> wrote:
> > > Thanks. Does Andrews point above still hold though, that 
> is, gotcha 
> > > and div1 nodes are NOT siblings since they don't share a common 
> > > parent ??
> >
> > Yes, the expression was void on both counts - Andrew spotted one 
> > mistake, I spotted another.
> >
> > Michael Kay
> > http://www.saxonica.com/
> >
> > >
> > > Fraser
> > >
> > > On 17/04/2008, Michael Kay <mike@s...> wrote:
> > > >
> > > > > Sorry for asking an XQuery question here, if there is a more 
> > > > > appropriate forum please let me know.
> > > >
> > > > talk at x-query.com
> > > >
> > > > >
> > > > > Anyway, a question relating to this simple XQuery has been 
> > > > > circulating on another group, but I am puzzled as to
> > > whether using
> > > > > // on a sequence is valid (see the return clause below).
> > > I tried in
> > > > > a couple of XQuery parsers (Saxon9 + the one built into
> > > XML Spy) and
> > > > > both return no results ??
> > > > >
> > > > > let $set := (
> > > > >     <div1>one   </div1>,
> > > > >     <div1 class="doc">two   </div1>,
> > > > >     <div1>three   </div1>,
> > > > >     <div1 class="doc">four </div1>,
> > > > >     <gotcha>START</gotcha>,
> > > > >     <div1>five   </div1>
> > > > > )
> > > > > return $set//gotcha/preceding-sibling::div1[@class="doc"][1]
> > > >
> > > > This is actually an XPath question. This path expands to
> > > >
> > > >
> > > 
> $set/descendant-or-self::node()/child::gotcha/preceding-sibling::div
> > > 1[
> > > > @class
> > > > ="doc"][1]
> > > >
> > > > Now, one of the elements in $set is a gotcha element, but
> > > none of them
> > > > has a child, or has a descendant with a child, named
> > > gotcha. Therefore
> > > > the expression selects nothing.
> > > >
> > > > You want $set/self::gotcha/....
> > > >
> > > > Michael Kay
> > > > http://www.saxonica.com/
> > > >
> > > >
> > >
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• References:
  • XQuery Puzzle
    • From: "Fraser Goffin" <goffinf@g...>
  • RE: XQuery Puzzle
    • From: "Michael Kay" <mike@s...>
  • Re: XQuery Puzzle
    • From: "Fraser Goffin" <goffinf@g...>
  • RE: XQuery Puzzle
    • From: "Michael Kay" <mike@s...>
  • Re: XQuery Puzzle
    • From: "Fraser Goffin" <goffinf@g...>