RE: XML Schemas: Best Practices ? Versioning

[Tony.Coates@reuters.com]

On 05/09/2001 19:56:47 Michael Brennan wrote:

>I  don't think 3 and 4 are reliable. #3 makes the incorrect assumption that
>"instance documents give the name and location of the associated schema". This
>is undoubtedly the prevalent case, but as sound entity resolution mechanisms
>gain more widespread use, I'm inclined to believe there will be less and less
>of  this. You cannot assume a consuming application is relying upon the
>"schemaLocation" attribute (or even paying any attention to it). I think
>changing the target namespace is the only reliable approach.

Once again, too much emphasis on the belief that everything should work even if there is no "schemaLocation" given.  I really believe that taking this view, which does not seem to be the view of the W3C people I've talked to, will just lead to more complication than is necessary.

>In  spite of the complications it poses, I think #2 is the best practice.
>True,  instance documents and schemas that include the relevant schema must
>change to  reference the new version, but that is often a good thing. You don't
>want those  references to indiscriminately change to reference a new schema
>without  assurance that there are no incompatibility issues. Indeed, by
>changing the  namespace, you can permit concurrent use of different versions of
>a schema,  allowing users time to migrate to the new version as compatibility
>is  assured.

The same is true if you insist on a versioned "schemaLocation".

     Cheers,
          Tony.
========
Anthony B. Coates
(1) Content Distribution Architect - Project Gazelle
(2) Leader of XML Architecture & Design - Chief Technology Office
Reuters Plc, London.
Tony.Coates@reuters.com
========



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