RE: [xml-dev] A single, all-encompassing data validation language - good

["Michael Kay" <mike@saxonica.com>]

> 5. Discourages competition.  Today there is a competition 
> among the schema languages.  A single language that does 
> everything may reduce the competition.

You're suggesting it's a bad idea to put this feature in XML Schema because
it will encourage more people to use XML Schema? Well, there's a certain
twisted logic in that, I suppose. But it's not the kind of argument that's
going to stop the development!

Assertions in schema are great. I've got a prototype implementation in Saxon
and have been playing with it, it's very powerful, especially as you can use
doc() to access external documents, you can call Java extension functions,
and so on. My only complaint is the spec doesn't go far enough, for example
assertions are defined on complex types but not on simple types.

Michael Kay
http://www.saxonica.com/