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

[Michael Kay <mike@saxonica.com>]

> 
> > 2. Is grammar validation of a fundamentally different 
> nature than rule validation?
> 
> I think so.

Say you've got a schema that says an element representing data for a month
must have at most 31 children, and you decide you want to be a bit more
precise and say it must be 30 for some months and 31 for others and
occasionally 28 or 29. Does this refinement mean you are doing something of
a fundamentally different nature? I think not. It does mean that you've
crossed the limits of what can be done with a grammar-based approach, but
surely we should make it as easy and seamless for people to cross that
boundary as we can?

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