W3C home > Mailing lists > Public > xmlschema-dev@w3.org > November 2005

unique constraint interpretation.

From: Tishkin, Eugene <etishkin@mackenziefinancial.com>
Date: Wed, 9 Nov 2005 09:31:14 -0500
Message-ID: <9685B8A36EB4A344A2AD0CC3508262C801DC6355@MFMAILEVS1.mackenziefinancial.bz>
To: <xmlschema-dev@w3.org>

Hi,

The below is the comment from Xerces parser BUG 18405 report:
================================================
"3 For each node in the
Ětarget node setĚ
all of the
{fields},
with that node as the context node, evaluate to either an empty node-set or a
node-set with exactly one member, which must have a simple type."

The target node set is the set of nodes on which the selector is matched.  Note
that this condition must hold for *any* identity constraint; only in bullet 4
of the tableau are the differences between key and unique described. 
Therefore, it seems clear that, if a selector matches, then either all of the
fields must match or none of them must match; even for xsd:unique, you can't
have some fields matching.
=========================================================

Especially I'm interested in the conclusion:

"Therefore, it seems clear that, if a selector matches, then either all of the
fields must match or none of them must match; even for xsd:unique, you can't
have some fields matching."

Is this a correct interpretation of unique constraint?

Regards,
Eugene





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Received on Wednesday, 9 November 2005 14:52:03 GMT

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