> Shouldn't it be the case that the validation process necessitates
> a 2-stage parsing ? What I mean is that XSD can only do a lexical
> validation, a second follow-up stage that validates against the
> application semantics is required.
That's actually four levels already: unicode encoding, XML well-formedness,
schema validity, and application validity. And yes, you often need multiple
levels.
But that doesn't stop you wanting individual levels to be configurable. A
very simple example, when I validate new documents I want to check that the
date is today. That kind of thing is very easily achieved by a configurable
schema. Equally, the application-level validation is often done using XSLT
stylesheets, and people often transform stylesheets for the same reason: you
need things to be configurable at that level too.
Michael Kay
