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RE: XQuery and DTD/Schema?

• To: "'David Carlisle'" <davidc@n...>,<mike@w...>
• Subject: RE: XQuery and DTD/Schema?
• From: "Michael Kay" <michael.h.kay@n...>
• Date: Wed, 3 Jul 2002 21:59:44 +0100
• Cc: <xml-dev@l...>
• Importance: Normal
• In-reply-to: <200207031639.RAA04310@p...>
• Reply-to: <michael.h.kay@n...>

> Even if XQuery (and XSLT2/XPath2) accept PSVI constructed by 
> means other than W3C Schema as input documents, the drafts 
> currently have strong bias towards W3C Schema in that the 
> validate expression requires (at my reading at least) a W3C 
> schema and similarly the types statically known to the query 
> are specified by schema import which again has to be 
> W3C schema, I think.
> 
There are a lot of open questions here. The schema import says that "it
imports element and attribute declarations and type definitions from a
schema". It doesn't say what language the schema has to be written in. I
think this leaves room for implementors to support mappings to other
schema languages - though I agree that the terminology (like the type
system itself) is heavily biased towards XML Schema.

The XQuery validate expression (which, I think, is likely to disappear
from XPath) does refer normatively to the semantics of validation as
defined in XML Schema. But all that it is really saying is that the
definition of whether an instance conforms to a type is to be found in
the XML Schema specification, which is implicit in saying that the type
system is based on that of XML Schema. It's quite possible, I think,
that we could abstract away from this by saying that an imported type
definition supplies its own validation method.

Michael Kay
Software AG
home: Michael.H.Kay@n...
work: Michael.Kay@s... 

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