xml-dev - RE: XML validation

["Arnold, Curt" <Curt.Arnold@hyprotech.com>]

The example you gave involved Microsoft's XDR schema language use of using namespace identifiers to bind documents to schema resources.  To the best of my knowledge, there is no ability in the
Microsoft MSXML Parsers to interact with the resolution of the XDR schema other than that provided in the platform and there are no other parsers available or anticipated that support XDR.  You may be
able to write a pluggable URL resolution protocol that would be used to resolve any URL reference and MSXML would probably use that to find the schema resource.  Basically, you would use a value like
"x-schema:timberline://ourschemas/bookschema.xdr" for xmlns and write and register a protocol handler for the "timberline" protocol.


The W3C XML Schema working draft's sections on locating schema resources is written from a perspective that dereferencing a URL in the instance document is the least likely mechanism of getting a
schema.  The more likely mechanism is this that a document will be validated against the schema the receiver anticipates instead of against the schema that the document asserts to which it conforms.

Since the XML Schema draft does not address parser API's how this is done in different parsers will probably vary.  However, you would expect that the complete implementations of XML schema will
provide the application a notification that it needs a schema resource for a particular namespace and any location hints from the instance, the application could then provide an alternative schema
resource.

I do not know if this behavior is currently available in any of the XML Schema implementations.