[xquery-talk] Schema in xquery

Michael Kay mike at saxonica.com
Tue Mar 6 00:41:03 PST 2012

On 06/03/2012 02:27, David Lee wrote:
> I've been contemplating the relationship between schema and type in schema aware xquery.
> Is xquery strictly tied to XSD? That is,  could an implementation support another schema format such as rng to provide for the type system?
It would be possible to support a different schema language, but not 
without difficulty.

(a) XSD is the only schema language I know of that defines how elements 
and attributes in the instance document are associated with types, and 
that includes constraints (such as the notorious UPA) to make this 
association unambiguous.

(b) Many of the concepts of XSD, such as the distinction between simple 
and complex types, substitution groups, and nullability, turn up in the 
semantics of XQuery, and would need to be mapped to the concepts of a 
different schema language.

Michael Kay

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