W3C home > Mailing lists > Public > xmlschema-dev@w3.org > January 2003

Re: Constraints in XML Schema

From: <noah_mendelsohn@us.ibm.com>
Date: Mon, 6 Jan 2003 18:19:46 -0500
To: Stefan Wachter <Stefan.Wachter@gmx.de>
Cc: Jan Mendling <mendling@web.de>, xmlschema-dev@w3.org
Message-ID: <OFF3591E52.4E07778E-ON85256CA6.00807780@lotus.com>

>> you are absolutely right that the expressiveness of XML
>> schema constraints should be improved

I agree.

>>  and XPath seems to be a natural option.

Yes, though certainly other options (Relax-like tree
automata, something else grammar-based, etc.) should at
least be considered before a decision is made.  I agree
that XPath is a likely good choice.

> About performance: I think performance matters should
> not guide the decision about wheter XPath-Constraints
> should be added to the schema specification or not. If
> performance is a matter then people can switch of
> validation (or use only simple constraints).

Here I respectfully but strongly disagree.  It's
essentially that my customers and those with whom they
do business get consistent results when they validate a
given document with a given schema.  If they say "Well,
it was valid with XYZ-Corp.'s high performanc processor
but not ABC's" we've got a mess.  The main reason to
use XML is universal consistency and interop.  High
performance schema processing is very, very important
to IBM's customers, as is consistency of semantics.  I
think we can get better co-occurrence constraints
without sacrificing performance.

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Noah Mendelsohn                              Voice: 1-617-693-4036
IBM Corporation                                Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
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Received on Monday, 6 January 2003 18:24:26 GMT

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