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> Thanks for the clarification, these are the things I was
> hoping someone could tell me, using for iterator etc, have we
> introduced more non-closed operators?? Has someone looked at
> them closely..?? I suspect there will be some more operators
> of this nature in XPath 2.0..
The input and output of XPath operations are constrained to be values
described by the XPath data model. In that sense the language is closed.
Whether the data model has the particular mathematical properties you
are looking for is something I can't easily judge.
There are a few glitches in terms of closure, for example I'm not very
comfortable with the fact that the semantics of FLWR expressions in
XQuery are defined using a notion of "tuples" which are objects that
can't be represented directly in the data model, but overall I think
it's pretty clean.