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RE: Restrictions on existence of attributes?

• To: Michael Kay <mike@s...>
• Subject: RE: Restrictions on existence of attributes?
• From: Eric van der Vlist <vdv@d...>
• Date: Wed, 28 Jun 2006 11:52:03 +0200
• Cc: xml-dev@l...
• In-reply-to: <00a701c69a95$d20ed5b0$1b09010a@turtle>
• Organization: Dyomedea (http://dyomedea.com)
• References: <00a701c69a95$d20ed5b0$1b09010a@turtle>

Le mercredi 28 juin 2006 à 10:32 +0100, Michael Kay a écrit :
> > 1) the error messages that you get when there are several 
> > attributes would be misleading for end users
> 
> That doesn't seem a convincing argument. Saxon says:
> 
> Validation error on line 1 column 20 of file:/c:/temp/test.xml:
>   Identity constraint {uniqueAtt}: the field selects more than one node (See
>   http://www.w3.org/TR/xmlschema-1/#cvc-identity-constraint clause 3)
> 
> Not exactly ideal for "end users", but it's no more obscure than the error
> messages for many other validation errors. 

No, I wish all schema processors could be so clear.

> > 2) W3C XML Schema processors differ in their interpretation 
> > of the spec on this point and this leads to interoperability issues.

Xerces-J which is not perfect but usually decent used to raise an error
(with a more obscure message than the one you've copied) but recent
versions (for a year of two) do not consider that as an error any
longer. 

> That's an even less convincing argument. If a schema processor doesn't
> conform to the spec, then don't use it.

I am not sure that this would leave any choice (except maybe Saxon) and
the best way to follow this recommendation would be to migrate to RELAX
NG!

More seriously, I have tried to fight so that my customers use only
conform implementations for years hoping that the situation would
improve but that's not the case. You can't deny that people have to live
with the choices they get whether these choices are conform to an
obscure recommendation or not. 

Eric
-- 
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Have you ever thought about unit testing XSLT templates?
                                                     http://xsltunit.org
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Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
(ISO) RELAX NG   ISBN:0-596-00421-4 http://oreilly.com/catalog/relax
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema
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