proposal for identifying optional features

Tony suggested we have some way of identifying which optional 
features or profiles a given implementation supports, or that a given 
request or policy requires.

We have survived without this through XACML 1.0 and 1.1, but if
we decide it is worth doing, here is a proposal.

create a urn for each profile or separate optional feature 
(e.g. obligations, xpath).  Create an optional element that can be 
included in a policy to list the required urn's.  For a request, I think 
we could just define an environment variable to hold the list of 
required urn's.  The format of the variable could be the same as the 
format of the optional element.  A context handler could be aware of 
that variable.  We also need to define error codes or other behavior if 
a PDP does not support required options.  We need to decide whether 
supporting the "optional support" feature is itself optional!

Anne
-- 
Anne H. Anderson             Email: 
Sun Microsystems Laboratories
1 Network Drive,UBUR02-311     Tel: 781/442-0928
Burlington, MA 01803-0902 USA  Fax: 781/442-1692