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Re: XQuery

From: Michael Dyck <MichaelDyck@shaw.ca>
Date: Thu, 01 Nov 2001 00:33:13 -0800
To: Frieda Shachar <fridas@cs.huji.ac.il>
Cc: www-ql@w3c.org
Message-id: <3BE108C9.A218862F@shaw.ca>
Frieda Shachar wrote:
>         Do you know if there's a way to compute in XQuery for
>         a given path expression all it maximal matching values
>         (meaning: for a given matc of a path is maximal if there is no
>          other match for a broader pattern of that path)
>         I'll be thankfull if you can refer me to one or few examples
>         which ilustrate what I've quesioned.

Uh, it would help if *you* could provide an example of what you mean.
(I'm particularly puzzled about the phrase "a broader pattern of that path".)

Here's a possible interpretation:
For a given path expression E, the _maximal_set_ of E (with respect to some
evaluation context) is the set of nodes N such that:
   N is in the nodeset selected by E (w.r.t. that context), and
   no ancestor of N is in that nodeset.

And yes, you can compute this in XQuery. For example:

    DEFINE FUNCTION maximal( nodeset $s ) RETURNS nodeset
        FOR $n IN $s
        WHERE empty( $n/ancestor::* INTERSECT $s )
        RETURN $n

-Michael Dyck
Received on Thursday, 1 November 2001 04:50:59 UTC

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