it's ggod becouse it's an standard. If some one (Microsoft, IBM, etc.) pretends pattents on this then maybe that "someone" should remember this, it's just a notation, SGML sub-set, and everyone is free to make functions to access any data structure (API').

what is missing here is Prolog and Lisp, maybe those languages could be used instead of XSLT, XQuery, this is what we really need, then is it necesary X#?