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   RE: xml spec 1.0 validity constraint for ID/IDREF

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  • From: Leigh Dodds <ldodds@ingenta.com>
  • To: Xml-Dev <xml-dev@xml.org>
  • Date: Wed, 29 Mar 2000 16:20:50 +0100

> -----Original Message-----
> From: owner-xml-dev@xml.org [mailto:owner-xml-dev@xml.org]On Behalf Of
> gopi
> Sent: 29 March 2000 12:57
> To: Xml-Dev
> Cc: tbray@textuality.com
> Subject: xml spec 1.0 validity constraint for ID/IDREF

[various questions regarding ID attribute type]

XML-DEV had a thread on this only recently see [1] for some 
related discussion.

> 	One more thing, I have not read xml schema spec in detail, 
> 	can anyone tell me whether this case is taken care there?

To quote Henry Thompson [2].

>XML Schema ... addresses both your requirements:

>  1) Multiple keys on a single element are OK;
>  2) Being (part of) a key is independent of your datatype.

So I believe XML Schemas better support your needs to map 
database keys to unique attribute values.

In the past I've avoided use of ID for many of the reasons 
you outlined, I used just 'ordinary CDATA' attributes. 
Additional checks at the application level are required 
to enforce the constraints however.

[1]. http://www.egroups.com/group/xml-dev/showthread.html?start=19179
[2]. http://www.egroups.com/group/xml-dev/19189.html



Leigh Dodds, Software Engineer       | "Pluralitas non est ponenda
http://weblogs.userland.com/eclectic |    sine necessitates"
http://www.xml.com/pub/xmldeviant    |     -- William of Ockham

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