Declarative constraints for XML documents

Rick Jelliffe ricko at
Fri Aug 20 12:57:57 BST 1999

 From: Arnold, Curt <Curt.Arnold at>

> Mike Spreitzer wrote:
> >>Declarative constraints are what schemas are for!

> The thread has followed a little convoluted path since I posted my
> query.  The original query was primarily targeted to currently available
> technologies to solve the specific problem, however I agree with you that
> the fundamental intention does fall under the requirements in the Schema
> working group and that the Schema would be an ideal place to express these
> constraints.

Your original question asked whether XSL could be used to express
I have an article on this subject "Using XSL as a Validation Language" at  The specifics in the
are out-of-date with the current XSL draft, because the article is about 7
old now.

For general discussion articles on the kinds of constraints you are are
talking about,
there are several articles at
Since you bring up "Facets", you may be interested in the notes:
    * Axis Models & Path Models: Extending DTDs with XPaths
    * Validate This! Content Models on Different Targets
    * Richer Anonymous Content Types

So far, the W3C Schema draft does not look at any kind of extended
validation: tree structures are nice, but surely we want to validate webs of

Rick Jelliffe
Academia Sinica Computing Centre
Taipei, Taiwan.

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