"Stateful XML protocol" makes complete sense, it just isn't very informative. It describes a protocol that is both stateful and XML-based. Those are independent attributes of a protocol; obviously, you can have both stateful non-XML-based protocols and XML-based stateless protocols, but I don't see why the OP's statement is nonsensical.

Totally agreed. That doesn't negate anything I just said. It's stateful. It's XML. It's a stateful XML protocol (and it happens to also have presence, which I left out, but does make some people's knickers wet).