Schema Optimsations Was XSL: For-Each Efficient or Not

On a related subject I have been thinking about what might be accomplished 
with schema information available at stylesheet compile time as apposed to 
runtime. Its long been speculated that there are many optimisations available 
in that scenario but I don't know of any processor that takes advantage of 
them today which is probably a big hint about the practicality of such 
schemes.

Given runtime schema information of the type proposed in XPath 2.0, it would 
appear to me that the performance cost of generating/using it may out way the 
benefit, potentially causing schema aware XSLT 2.0 processors to be slower 
than 1.0 ones.  

The best alternative I can think of is to compile stylesheets against a 
specific schema. So there may be many compiled forms for a single stylesheet. 
But even this case has problems, just because a document says it uses a 
schema is no help if its not being validated, which I can't see being cheap 
with any schema language.

I guess the question is, how do you write a schema aware processor that is 
quicker than a schema ignorant processor?

Kev.



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