Hal,
Are you suggesting that there is merit in including
the capability to identify the right policy
("identify" is presumably a service "some" PDP can provide)
for a specified target (let us assume that we will solve the target
specification problem in XACML) within the scope of XACML charter?
Or are you suggesting that XACML should include syntax that will allow
interpretation and selection of a single policy from a set of policies?
Does SAML expect to use XACML in that way?
-Suresh