version of schema on include

Hi,

       Has any consideration been given to adding a "version" attribute on
the "include" element in schemas? The "schemaLocation" URI is a hint to the
schema processor, and the version number would be an (optional) additional
hint. If present, and used, this version number could be matched up against
the version declared for the included schema thereby allowing a validating
schema parser the ability to perform an additional sanity check.

Thanks,
Kenneth