RE: [xml-dev] Rick Jelliffe quotable quote on the purpose of schemas

• From: "Michael Kay" <mike@...>
• To: "'Philippe Poulard'" <Philippe.Poulard@...>,"'Costello, Roger L.'" <costello@...>
• Date: Mon, 11 Dec 2006 15:30:08 -0000

> "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/