Yet Another V2 Request: Extension Functions via XSLT 2

It sure would be handy to be able to define functions that can be used in
step expressions via XSLT 2.  Specifically, I'm thinking of things that
control p:choose alternatives.

My use case is simply calculating the type URIs for an RDFa typeof
attribute.  I want to process a document differently depending on an RDFa
typeof attribute.  The type value is a resolved by a number of operations
that neatly fit into an XSLT function definition.

Right now I have to wrap this in an p:xslt step that outputs a coded
document that I can use the p:choose step.  If I just had the function
available, I could run it directly.

The feature could only be available if an implementation supported XSLT 2.

Thoughts?

-- 
--Alex Milowski
"The excellence of grammar as a guide is proportional to the paucity of the
inflexions, i.e. to the degree of analysis effected by the language
considered."

Bertrand Russell in a footnote of Principles of Mathematics