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Re: Schema being imported multiple times

From: Eric van der Vlist <vdv@dyomedea.com>
Date: Wed, 10 Oct 2001 17:03:32 +0200
Message-ID: <3BC46344.1050502@dyomedea.com>
To: "Nguyen, Thang" <nguyet3@anz.com>
Cc: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>

Nguyen, Thang wrote:

> I'm using MSXML4.dll (Visual Basic 6) and schema validation.  When I create
> Schema1.xml and validate it with VB, it's fine but when I create Schema2.xml
> and validate, it comes up with an error   "  The '{urn:Common}
> RevisionNumber' element has already been declared"
> (but the validation is successful withing XML Spy)
> This is because Common.xsd is being pulled into the SchemaCache twice (once
> from Schema2.xsd and once from Schema1.xsd).
> is there a way to work around this error?

I don't know how to workaround it with MSXML4, but it's a bug for a 
validator to give this error even though it is considered as a bad 
practice for an application to include multiple schema imports for a 
same namespace.

The rec says it in plain English:


"NOTE: The above is carefully worded so that multiple <import>ing of the 
same schema document will not constitute a violation of clause 2 of 
Schema Properties Correct (§3.15.6), but applications are allowed, 
indeed encouraged, to avoid <import>ing the same schema document more 
than once to forestall the necessity of establishing identity component 
by component. Given that the schemaLocation [attribute] is only a hint, 
it is open to applications to ignore all but the first <import> for a 
given namespace, regardless of the ·actual value· of schemaLocation, but 
such a strategy risks missing useful information when new 
schemaLocations are offered."

Hope this helps.


> Thanks

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Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
http://xsltunit.org      http://4xt.org           http://examplotron.org
Received on Wednesday, 10 October 2001 11:03:10 UTC

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