> "The flaw with grammars is that they only allow to constraint
> content models in a declarative manner
There's nothing wrong with constraints being declarative - in fact, they
definitely should be - the flaw is with the expressive power of a grammar as
a contraint language.
This is all well known. And in fact, XML Schema itself has some
extra-grammatical constraints, namely uniqueness and referential
constraints. But there's still a camp that believes (wrongly, in my view)
that the expressive power of a schema language should be restricted for
performance reasons.
Michael Kay
http://www.saxonica.com/
