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Re: XPath 2.0

Subject: Re: XPath 2.0
From: David Carlisle <davidc@xxxxxxxxx>
Date: Tue, 8 Jan 2002 21:59:36 GMT
preciding xpath
>      xf:id('a1') precedes xf:id('a2')
> would raise an error because xf:id() returns a sequence,

I think not, as there is no distinction in the data model between a
value and a sequence of length one containing that value. (Essentialy,
everything is a sequence in xpath2 as currently spec'd)

> (b) if nodes with ids a1 and a2 exist in the tree being queried,
>      xf:id('a1')[1] precedes xf:id('a2')[1]
> is equivalent to
>      xf:exists( xf:id('a1') intersects xf:id('a2')/preceding::* )

Yes, I think (which means really preceding is just redundant given the
preciding axis.

> And similarly
>      xf:id('a1')[1] << xf:id('a2')[1]
> is equivalent to
>      xf:exists( xf:id('a1') intersects ( xf:id('a2')/preceding::* | xf:id('a2')/ancestor::* ) )
yes if they are in the same tree but not if they are in different trees
(I think)

> because a non-empty sequence would automatically be treated
> as the boolean value true.
somewhat regretably that has gone, as a consequence of the
feature above that a boolean value of false() is equivalenet to a
sequence of length one containing that value, and this is clearly non

(answers just based on my reading of the drafts,  I'm not on the WG so
don't trust me:-)

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