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RE: Identity Constraints

From: Mark Thornton <mthornton@optrak.co.uk>
Date: Fri, 8 Mar 2002 17:26:36 -0000
Message-ID: <30273167BD5AD111A5AD00A0C9922017537468@mercury.net.optrak.co.uk>
To: "'priscilla@walmsley.com'" <priscilla@walmsley.com>, xmlschema-dev@w3.org
I can well understand the problems with allowing ancestor in xpath
expressions for a streaming processor (as mine is). My current fudge is
based on the erroneous example in the primer, but if I ever get time I'll
try to convert the implementation to use .. instead (harder to implement,
but the intent is much better defined).

Regards,
Mark Thornton

-----Original Message-----
From: Priscilla Walmsley [mailto:priscilla@walmsley.com]
Sent: 08 March 2002 15:21
To: 'Mark Thornton'; xmlschema-dev@w3.org
Subject: RE: Identity Constraints


Hi Mark,

We did consider it - in fact, earlier drafts of the recommendation allowed
you to reference an ancestor (..), which would have met your needs in this
case.  In the end, it came down to defining a manageable subset of XPath
that could reasonably and unambiguously be implemented by schema processors
for Version 1, and the ancestor function was removed.  The working group is
aware that this is a limitation for multi-part keys, and is considering it
as a future requirement.

Thanks,
Priscilla

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Priscilla Walmsley                          priscilla@walmsley.com
Vitria Technology                            http://www.vitria.com
Author, Definitive XML Schema                  (Prentice Hall PTR)
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Received on Friday, 8 March 2002 12:27:15 GMT

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