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RE: Versioning of XML Schema and namespaces

From: Michael Kay <mike@saxonica.com>
Date: Fri, 6 May 2005 11:25:44 +0100
To: <John.Hockaday@ga.gov.au>, <xmlschema-dev@w3.org>
Cc: <":www-xml-schema-comments"@w3.org>
Message-ID: <E1DU01w-0003y6-Bs@maggie.w3.org>

> I found that the first draft of ISO 19139 was not valid.  It 
> hopefully will
> be valid in the final release.  The other problem is that I don't have
> control over how ISO 19139 identifies its schemalocation.  
> Can I trust that
> an International Standard will have versions in its schema 
> locations? 

I don't know anything about this particular standard, but I would expect a
spec like this

(a) to remain backwards compatible from one version to the next

(b) therefore, to continue using the same namespace from one version to the

(c) to include some kind of mechanism for identifying which version of the
standard an instance claims to conform to, such as a version attribute
within the instance.

I would then expect a recipient to read the version attribute, and to invoke
validation against an explicitly selected schema loaded from a known and
trusted location. Alternatively, a recipient might require that the instance
conforms to a specific version and simply load the schema for that version
from a known and trusted location.

I wouldn't expect the instance document to contain a schemaLocation
attribute, or if it does, I wouldn't expect a recipient to trust it when
doing validation. If say the sender has decided to leave out some mandatory
elements, and to create a local copy of the schema that makes them optional,
you as the recipient don't want validation to succeed.

Michael Kay
Received on Friday, 6 May 2005 10:26:02 UTC

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