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

[Christian Grün]

Geert,
I have checked your test cases; imho, all of them are correct.

Christian


2009/3/28 Geert Josten <Geert.Josten at daidalos.nl>:
> Yes,
>
> It starts making sense to me now as well. I keep forgetting that $xml/p actually means $xml/child::p. And we all understand intuitively what $xml/p[2] means (especially when reading it as $xml/child::p[2])..
>
> Just for the sake of completeness, I wrote a simplistic self-contained testsuite with most interesting cases. If someone of you lot could just take a look whether I didn't make any mistakes, that would be appreciated.
>
> Kind regards,
> Geert
>
>>
>
>
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>> From: talk-bounces at x-query.com
>> [mailto:talk-bounces at x-query.com] On Behalf Of Ronald Bourret
>> Sent: vrijdag 27 maart 2009 21:53
>> To: Pavel Minaev
>> Cc: talk at xquery.com
>> Subject: Re: [xquery-talk] Question on expected XQuery return
>> per standards
>>
>> Pavel Minaev wrote:
>> > On Fri, Mar 27, 2009 at 12:06 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 it isn't. The standard is very clear that $xml//p expands to
>> > $xml/descendant-or-self::node()/p. The ordering is also very clear:
>> >
>> >   "Each non-initial occurrence of "//" in a path expression is
>> > expanded as described in 3.2.4 Abbreviated Syntax, leaving
>> a sequence
>> > of steps separated by "/". This sequence of steps is then evaluated
>> > from left to right."
>> >
>> > and, obviously, in $xml/descendant-or-self::node()/p[2], 2 is the
>> > position within the sequence of child nodes of the parent of p, not
>> > the expression as a whole.
>>
>> Thanks for the clarification. I had to think about it a bit
>> -- the parent isn't obviously involved until you realize that
>> the parent is a descendant of $xml -- but that now makes sense.
>>
>> -- Ron
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-- 
___________________________

Christian Gruen
Universitaet Konstanz
Department of Computer & Information Science
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