Re: XQuery and DTD/Schema?
At 09:31 AM 7/3/2002 -0700, Tim Bray wrote: >At the moment this latter assumes that the schema validation is done by >XSD because as far as I can tell nobody ever asked for the ability to use >a different validation facility. I see no architectural reason why you >couldn't add an argument or environment variable or something >saying "here's the identifier of the schema language I'm using". > >It's going to be tough to tear XQuery away from XML Schema's base data >types, and probably not worth doing; they ain't perfect but the code to >deal with them is written and out there, so why fight it. Note that XSD >base types are effectively built-in to RELAX software too these days. > >Beyond that, I see no architectural difficulty in making XQuery >schema-language agnostic. -Tim Making a query language agnostic with respect to the underlying model is fairly difficult, and the devil is in the details. RELAX-NG uses purely structural typing. XML Schema uses named typing, as does XQuery (for the most part). There is no problem supporting RELAX-NG as well-formed XML with datatypes, but you would have to define a mapping that creates type annotations for the simple types. If you want XQuery to support the structure of elements, you would have to create type annotations for these as well. I think all of this could be done, but this would require someone to sit down and do a fair amount of work. There are some aspects of RELAX-NG which XQuery would not support, such as co-occurrence constraints. Jonathan
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