RE: [xml-dev] Is Schematron (using XPath 2.0) functionally a superset of

["Michael Kay" <mike@saxonica.com>]

> 
> Is Schematron (using XPath 2.0) functionally a superset of 
> XML Schemas?

Remember that XML Schema does more than validation.

Even if you're only interested in validation, then I think there are some
rules that can be expressed in a grammar that are very hard to express in
predicate calculus. Even simple rules like a content model of (name,
address-line+, postcode) are very clumsy to express as XPath assertions,
though it can be done. I don't know the answer to the theoretical question
of whether all grammar rules can be translated into predicates, but I know
that the answer to the practical question is that I wouldn't want to.

Michael Kay
http://www.saxonica.com/

> 
> Using XPath 2.0, Schematron can now perform all of the 
> grammar-type checks that XML Schemas does, e.g. check that 
> the correct tags are being used, the tags are arranged 
> properly, and the datatypes of each element and attribute are 
> correct. 
> 
> Plus Schematron can perform co-constraint checks, cardinality 
> checks, and algorithmic checks that XML Schemas cannot do.
> 
> Are there things that XML Schemas can do that Schematron (using Xpath
> 2.0) cannot do?
> 
> /Roger 
> 
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