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Re: keyref with empty sets

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Wed, 02 Jun 2004 09:35:34 +0100
To: "Zafar Abbas" <zafara@microsoft.com>
Cc: "Nigel Hardy" <nwh@aber.ac.uk>, <xmlschema-dev@w3.org>
Message-ID: <f5bu0xufjc9.fsf@erasmus.inf.ed.ac.uk>

"Zafar Abbas" <zafara@microsoft.com> writes:

>>Basically, the REC (correctly, in my view) imposes _no_
>>requirements on keys if there are no hits for a keyref
>>From my reading of the clause below, it does seem that the content
> selected by a key _must_ exist in the content, and if someone wanted to
> have null keys, one would use xs:unique.
> structures spec section 3.11.1:
> {key) the Identity-constraint definition asserts uniqueness as for
> unique. key further asserts that all selected content actually has such
> tuples.

Right -- that says _if_ an element is selected by a key's select
pattern, it _must_ have the necessary field(s).  But if (as in the
example we're working with on this thread) there are no selected
elements, there's no problem.

So, no keyref selections, no key selections, no problem.

 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Wednesday, 2 June 2004 04:35:45 UTC

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