I think XACML has benefitted from having a relatively clear model of the relationship between the PEP and the PDP. In particular it has guided decisions about what aspects to standardize and what to leave unspecified.

Currently the PAP concept is pretty vague. I think we need to break it up into subcomponents and define their relationships. This will give us the ability to decide what aspects should be standardized, what properties the components are required to implement and where the opportunities for unstandardized value add are.

I therefore agree with Danny that we should split off the policy management aspects into a different profile and drive the REST-based decision request to completion. I am uncertain whether this should wait on the JSON representation or that should be put off to a later version. An additional possible advantage of this approach is that it may be prove much simpler to specify the Request in JSON than the policy language.