Title: RE: [xacml] Comparing ACME with WS Policy framework Anne - Thanks for the response. Your comments are very valuable. For me, the main "take-away" is that XACML focuses exclusively on one type of policy-consumer - the most important one, of course. That is the PDP; whose job it is to render a "decision". I expect that all policy architectures contain a PDP. But, many policy architectures also contain alternative policy-consumers. Some of these alternative policy-consumers have to combine policies, not just decisions (as PDPs are required to do). In the general case, combining policies is not practical. However, I expect that under carefully-chosen conditions, it IS practical (indeed, the WSS-QoP whitepaper describes precisely how to do this in one circumstance of practical interest). There is nothing in XACML that inherently prevents it serving this purpose. To the best of my knowledge it is no more limited in this respect than the other candidate policy languages. So, it is legitimate to ask "how must XACML adapt to accommodate the requirement to combine policies?" Prima facie, the changes required are modest: profiles are required that prescribe the large-scale logical structure of a policy statement (e.g. AND of ORs) and the existing combining algorithms have to be extended to describe how policies are combined in these profiles. I put these thoughts forward in the spirit of fostering debate, not because I am convinced that this is the best way to proceed. Some of XACML's main strengths are its recognition that combining of some form is required and its rich and well-understood set of operators. I would hate to see us dismiss it as a basis for solving other problems because we didn't fully appreciate its strengths relative to other proposals. All the best. Tim.