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RE: Identity Constraints

From: Mark Thornton <mthornton@optrak.co.uk>
Date: Fri, 8 Mar 2002 14:20:12 -0000
Message-ID: <30273167BD5AD111A5AD00A0C9922017537467@mercury.net.optrak.co.uk>
To: "'priscilla@walmsley.com'" <priscilla@walmsley.com>, xmlschema-dev@w3.org
Thanks,
	while I am glad that I had interpreted the standard correctly, I am
also disappointed that the functionality I seek isn't available. As it
happens this problem occurs with a processor I wrote myself so I have
extended it to do what I want. As you might expect the column names aren't
globally unique, and adding the table name as an attribute to each column
then requires a check that all the columns in a particular table actually
specify that table name and not some other name.

Do you know if the schema standard authors considered this type of identity
constraint and, if so, why it was rejected?

-----Original Message-----
From: Priscilla Walmsley [mailto:priscilla@walmsley.com]
Sent: 08 March 2002 13:58
To: 'Mark Thornton'; xmlschema-dev@w3.org
Subject: RE: Identity Constraints


Hi Mark,

You're right - that's a known issue with the recommendation [1]. It will be
listed in the errata.  I agree with Jeni that you are going to have
difficulty expressing exactly what you want to express using XML Schema,
unless the column's "name" attributes are unique across all table elements.
You could replicate the table name as an attribute on the column name, e.g.

<column tableName="addresses" name="street"/>


Hope that helps,
Priscilla

[1] http://www.w3.org/2001/05/xmlschema-rec-comments#pfiPrimerIDConst


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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 09:20:47 GMT

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