Looking at the other comments, I realize you're looking for object/XML mapping. My opinion is that this is pointless (and I'm guilty of applying it back in the SOAP days, too), because objects are co-inductive data structures based on the types of programming languages, whereas XML is based on grammars eg. a description of a class of sequences of content tokens.

Sure you can represent objects, ie. a memory dump of a running program, as XML, but what's the point?