Do problems about types and semantics arise with REST and POX? Of course they do. But, and this is the point that is skipped over by the WS-* salesmen, the same problems arise with WS-*. The very point of a service-oriented architecture is that you’re cleaving a very complex domain into a set of subdomains with different responsibilities; the complexity of negotiating what travels across the borders between those domains is an essential, not accidental, characteristic. In the face of such complexity, the best architectural choice is the one that provides the most visibility, so that problems and ambiguities can be quickly identified and addressed.