> In a testing application I'm writing, I have a need to 
> 1.validate  a given ID value as being a valid qname.

The current version of Saxon has a static method
com.icl.saxon.om.Name#isQName() which should be very easy to call from XSLT.
> 
> 2. I also need to validate a uri + fragment as being valid.

I've come to the conclusion that isn't possible. A URI is only valid if it
uses a protocol name that has been registered, and the set of registered
protocols changes with time. Saxon allows any string to be used as a URI,
until it's dereferenced, at which point it must be a URL acceptable to Java.

Mike Kay 

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