> 1) Although most widely used schema validators are fairly 
> slow, one can in 
> fact implement the XML schema rules at quite high speed.  My team is 
> hoping to publish some work in that area in coming months, 
> and I suspect 
> that others in the industry are working in the same 
> direction.  I think 
> it's important to the success of any technology we choose 
> that it be able 
> to meet the performance needs of our customers.

I would resist this kind of thinking. SQL was successful because it put
functionality first, and left implementors to devise optimisation
strategies. Users need a constraint language that is capable of expressing
arbitrary constraints on the content of a document, and it should be left to
the implementor to work out which of these constraints can be evaluated in
streaming mode and which can't.

SQL today allows the full power of the query language to be used to express
integrity contraints, and users learn when they need to restrict their
ambitions to meet performance requirements. 90% of applications aren't
performance critical anyway.

There's no point telling users to go and use some other technology to do
their validation, the other technology isn't going to be fast either.

Michael Kay



From brs@i... Thu Nov 17 10:02:23 2005
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