RE: Relax NG, Thoughts, etc.
> Granted, dynamic validation (=at runtime) is always possible, > but it is > certainly not a big help. Errors are discovered after having gone to > production, doesn't sound good to me. Actually, it's an enormous help compared with not doing it at all. I agree that static checking, where possible, is even better. Saxon doesn't do any static checking against a schema yet. > I am sure you will not try to add exact static typing based > on Relax NG for XSLT in the next version of Saxon? No, but I wouldn't rule it out eventually. > There are papers that analyze > this for subsets of XSLT Can you give me a reference? I'm not aware of such papers. > but doing it exactly, for the full > language, > is - as far as I remember - undecidable. Even with XML Schema, it's unprovable that a given stylesheet is guaranteed to create valid output (to do strict static typing, in the style of the XQuery static typing option, we would have to throw out xsl:apply-templates). But pragmatically, I think it's possible to give static warnings for a good proportion of user errors. And I suspect that most of the heuristics to do this are equally applicable to DTDs or Relax NG. Michael Kay
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