Hi Rick,
On Fri, 2003-08-08 at 13:01, Rick Jelliffe wrote:
> I have been aware of Robert's interest in this area for more than
> six months (he published his Schematron analysis quite
> a while ago and I worked through it then), and no-one should panic
Yes. I have found this interestesting and he did honestly stressed out
the fact that it was not meant to be a criteria to judge schema
languages. I see it more as a demonstration of how difficult the issue
of "Schema Conformance" is.
On the interest of SCP for end users, I think that it's not unlike
wanting to design a programming language in which people could *never*
do any stupid think such as programming an endless loop or a test that
can't be verified in a "if" statement and impose that this should be
easy to check for implementation. The aim may seem legitim but the
result would likely loose so much expressive power that the language
would get impossible to use for practical work.
> Please note that, on a related issue, probably any grammar-based schema
> language
> that allows fixed keys (such as ID #REQUIRED) is also NP hard. This means
> DTDs and W3C XML Schemas.
Yep. He has also shown that for RNG with WXS datatypes, SCP is NP hard
because of the pattern facet (and Murata Makoto has shown that SCP for
RNG withouth WXS datatypes is just linear) and that for WXS is was just
undecidable.
Eric
--
Have you ever thought about unit testing XSLT templates?
http://xsltunit.org
------------------------------------------------------------------------
Eric van der Vlist http://xmlfr.org http://dyomedea.com
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema
------------------------------------------------------------------------
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Received on Fri Aug 8 13:28:15 2003
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