RE: What is the Vocabulary of an Intersected Policy

Again, because absence is negation, doesn't the meaning of the
intersection result depend upon the vocabularies used as input to the
intersection?  That's how one could derive that you must remember
assertion types.  
 
If your point is that our definition of policy vocabulary is strict
enough that it means that "vocabulary" doesn't make sense to apply to a
policy intersection result, then that might be fair in which case we
might need "policy pre-intersection vocabulary" and "policy
post-intersection vocabulary" terms or the rough equivalents.
 
Cheers,
Dave


________________________________

	From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Fabian Ritzmann
	Sent: Monday, April 23, 2007 10:50 AM
	To: Ashok Malhotra
	Cc: ws policy
	Subject: Re: What is the Vocabulary of an Intersected Policy
	
	
	Hi,
	
	I don't want to get into the proposed solution because I think
the premise isn't entirely right. Ashok summarizes:
	
	

		Now, what is the vocabulary of this policy ?   Looking
at this policy alone it should be { A, B}. 

		BUT, Chris points out the vocabulary should be {A,B,C,D}
to remember the fact that this was the union of the vocabularies of the
two intersected policies and that {C. D} must not be applied since they
were not selected. 


	This is the definition of policy vocabulary:
	
	A policy vocabulary is the set of all policy assertion types
<http://dev.w3.org/cvsweb/%7Echeckout%7E/2006/ws/policy/ws-policy-framew
ork.html?content-type=text/html;charset=utf-8#policy_assertion_type>
used in a policy.
	
	
	I don't see how one could derive from there that you must
remember policy assertion types from a policy that served as input to
intersection. The policies that are the input for the intersection and
the policy that is the result of the intersection are different
entities. Each has their own policy vocabulary.
	
	Fabian
	
	
	Ashok Malhotra wrote: 

		We spoke briefly about this on the call today and I see
a problem. 

		This note is an attempt to state the problem clearly . 

		Consider two normalized policies: 

		<Policy> 

		    <ExactlyOne> 

		        <All> 

		              <A/> 

		               <B/> 

		        </All> 

		         <All> 

		                <C/> 

		         </All> 

		      </ExactlyOne> 

		</Policy> 

		< Policy> 

		    < ExactlyOne> 

		        <All> 

		              <A/> 

		               <B/> 

		        </All> 

		         <All> 

		                <D/> 

		         </All> 

		      </ExactlyOne> 

		</Policy> 

		Let us intersect these two policies.  What we get is: 

		<Policy> 

		    <ExactlyOne> 

		        <All> 

		              <A/> 

		               <B/> 

		        </All> 

		    </ExactlyOne> 

		</Policy> 

		Now, what is the vocabulary of this policy ?   Looking
at this policy alone it should be { A, B}. 

		BUT, Chris points out the vocabulary should be {A,B,C,D}
to remember the fact that this was the union of the vocabularies of the
two intersected policies and that {C. D} must not be applied since they
were not selected. 

		This seems like a contradiction.   To remember the
negative decision we need to include assertions that are not in the
policy , in its vocabulary. 

		SOLUTIONS: 

		The only viable solution that I can se e is to drop the
' negation ' semantic, namely, " When an assertion whose type is part of
the policy's vocabulary is not included in a policy alternative, the
policy alternative without the assertion type indicates that the
assertion will not be applied in the context of the attached policy
subject."   (Dale was arguing for this on other grounds as well)   Some
would object strongly to this.  A counter proposal would be to add an
explicit NOT operator. 

		Unfortunately, these are radical suggestions but I do
not see any other way out.   

		All the best, Ashok