[xquery-talk] Question on expected XQuery return per standards

David Sewell dsewell at virginia.edu
Fri Mar 27 15:35:25 PST 2009


For MarkLogic (4.0-4), sets 1 and 2 return the same as set 5 (only p2).
In other words, [position() eq 2] is parsed differently from [2].

Before filing a bug report I wanted more input, as this seems to be an
area where informed people disagree about the standard. So I'm
temporarily resisting my default behavior of assuming that whatever
Michael Kay says must be true. :-)

David

On Fri, 27 Mar 2009, Vyacheslav Sedov wrote:

> exist 1.2.5 - set 4 is same as set 5 :(
> anybody can check 1.3?
> i did not get yet latest 1.3 from svn
> Also would be helpful same info about Marklogic.
>
> 2Ronald for your case you can use brackets <set4>{ ($xml//p)[2] }</set4>
>
> With best wishes,
> Slav
>
> On Fri, Mar 27, 2009 at 10:06 PM, Ronald Bourret
> <rpbourret at rpbourret.com> wrote:
> > Hmmm. I would have thought that, in each case, only p2 is returned.
> >
> > According to the spec, "For each item in the input sequence, the predicate
> > expression is evaluated using an inner focus, defined as follows: The
> > context item is the item currently being tested against the predicate. The
> > context size is the number of items in the input sequence. The context
> > position is the position of the context item within the input sequence."
> >
> > In each case, the input sequence is the result of $xml//p, which is a
> > sequence of four p elements. Since the position is the position within this
> > sequence, only p2 is in the second position.
> >
> > But I'm sure I could be wrong...
> >
> > -- Ron
> >
> > David Sewell wrote:
> >>
> >> Over on another list there has been a discussion of unexpected results
> >> from an XQuery like the following. The issues are how the parser
> >> interprets, in particular, the abbreviated syntax '//' and '[N]' as an
> >> equivalent to '[position() eq N]'.
> >>
> >> My belief is that the standard requires that two nodes (p2, p4) should
> >> be returned for result sets 1-4 below, because the interpretation of the
> >> XPath should in each case be identical. Set 5, on the other hand, should
> >> return only p2.
> >>
> >> We're seeing different behavior from a couple of XML parsers. Anyone
> >> care to read from the stone tablets on this one?
> >>
> >> (: begin query :)
> >>
> >> let $xml :=
> >>  <root>
> >>    <div>
> >>      <p>p1</p>
> >>      <p>p2</p>
> >>    </div>
> >>    <div>
> >>      <p>p3</p>
> >>      <p>p4</p>
> >>    </div>
> >>  </root>
> >>
> >> return (
> >>  <set1>{ $xml/descendant-or-self::node()/p[position() eq 2] }</set1>,
> >>  <set2>{ $xml//p[position() eq 2] }</set2>,
> >>  <set3>{ $xml/descendant-or-self::node()/p[2] }</set3>,
> >>  <set4>{ $xml//p[2] }</set4>,
> >>  <set5>{ $xml/descendant::p[2] }</set5>
> >> )
> >>
> >> (: end query :)
> >>
> >> David S.
> >>
> >>
> >>
> >> ------------------------------------------------------------------------
> >>
> >>
> >> No virus found in this incoming message.
> >> Checked by AVG - www.avg.com Version: 8.0.238 / Virus Database:
> >> 270.11.30/2026 - Release Date: 03/27/09 07:13:00
> >>
> > _______________________________________________
> > talk at x-query.com
> > http://x-query.com/mailman/listinfo/talk
> >
>

-- 
David Sewell, Editorial and Technical Manager
ROTUNDA, The University of Virginia Press
PO Box 801079, Charlottesville, VA 22904-4318 USA
Courier: 310 Old Ivy Way, Suite 302, Charlottesville VA 22903
Email: dsewell at virginia.edu   Tel: +1 434 924 9973
Web: http://rotunda.upress.virginia.edu/


More information about the talk mailing list