I'm not following this group from the very beginning, and I do not remember a discussion about XML as a rendering option. Maybe Andy or Thijs have a record about this. JSON appears as more compact wrt XML, but probably XML has a richer set of utilities and is overall more established: any other relevant difference? There is an ongoing effort on a JSON rendering.

I think that schemas are unable to capture certain semantic aspects of OCCI specs, so their application, while useful, is not sufficient. Certainly the availability of libraries for navigating complex/deep structures is relevant.