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RE: Revised positions for closed/open world assumptions

From: Rogers, Tony <Tony.Rogers@ca.com>
Date: Tue, 15 May 2007 12:52:10 +1000
Message-ID: <BEE2BD647C052D4FA59B42F5E2D946B35C93D8@AUSYMS12.ca.com>
To: "Dale Moberg" <dmoberg@us.axway.com>, "Christopher B Ferris" <chrisfer@us.ibm.com>, <public-ws-policy@w3.org>
I hesitate to add to the confusion, but I had an idea.
 
Thinking from the point of view of a client, I know what assertions and
alternatives I included in my policy (let us be conventional, and posit
that I had assertions A, B, and C in my policy, and let us assume that
the intersection with the server policy includes only A and B).
 
Then I think I can make three statements:
 
1. I can definitely use the behaviours associated with assertions A and
B, because I "asked" about them, and they appeared in the intersection.
 
2. I can definitely NOT use the behaviour/s associated with assertion C,
because I "asked" about it, and it did not appear in the intersection.
 
3. I do not know if the server supports the behaviour/s associated with
assertion D, because I didn't "ask" about it. However, it would be
unreasonable to expect to use these behaviours because I didn't "ask"
about it. If I wish to use D's behaviour/s, I should have included it in
my policy.
 
Is that a reasonable way to look at the problem? It seems to me that the
discussions of open and closed worlds can be reduced to the space of the
assertions about which I (as client) "ask". If I don't ask about
something, then I don't know if it is supported or not, but it seems
unreasonable to expect it to be supported without "asking". I guess we
could say that there is nothing to stop the client attempting to use
such a behaviour, but it should be prepared to have it "fail" (for some
meaning of "fail").
 
Note that I do not posit the client inspecting the server's policy
statement - that could be done, but it could also be that the client
sends its policy to the server, and receives the intersection in return
(the server might not publish its complete policy statement).
 
Tony Rogers
tony.rogers@ca.com <blocked::mailto:tony.rogers@ca.com> 
 

________________________________

From: public-ws-policy-request@w3.org
[mailto:public-ws-policy-request@w3.org] On Behalf Of Dale Moberg
Sent: Tuesday, 15 May 2007 3:40
To: Christopher B Ferris
Cc: public-ws-policy@w3.org
Subject: RE: Revised positions for closed/open world assumptions



Chris Ferris writes:

Maryann and I have been noodling on language that tries to capture our
intent better. So, rather than 
add the "No other behaviors are to be applied" language, we think that
maybe if we added the following 
prose to section 4.5 Intersection, just before the algorithm is
described, that that might clear up the confusion 
while at the same time preserving the semantic that we believe to be
important. 

New text for section 4.5: 

If the intersection algorithm produces a policy alternative, common to
both parties, it indicates that the behaviors 
implied by the assertions in that policy alternative are an implicit
contract and will be applied for any interaction 
based on that alternative. Any behaviors not represented by policy
assertions in that alternative are out of scope 
and not applied as a result of policy framework processing.

 

DaleMoberg>> OK, by switching to an explanation of a "policy processing
model," I think a lot of the "logical quibbles" can drop out, and that I
think is an improvement. The language is not encroaching on the semantic
options that domain policy assertion designers have available. 

 

It seems that the advice actually gets close to common sense now, for
you appear to be saying that once you select a policy alternative,
engage in the behavior that you intend to engage in! 

 

The other alternatives are "out of scope" once your policy alternative
(for which you found a match) is selected. And if you included behavior
that triggered other provider-supported policy assertions (present in
other alternatives), then the other side can be expected to make a
response, and you might not be prepared for it! Or something like that
might occur that messes up the interaction. 

 

The phrase "implicit contract" though seems a stretch. Suppose the
policy provider offers several policy alternatives. The policy provider
presumably does not care what policy alternative is selected by the
policy consumer, and unless the provider was being deceptive, permits
the consumer to jump from one alternative to another. Is there any
presumption that in the case where several policy alternatives are in
common between consumer and provider, that the consumer cannot engage
one set of behaviors one time and another set of behaviors the next
time? I personally can't understand how to get that commitment over time
out of ws-policy at present. If the commitment is just for one time,
then the advice boils down to the truism, that a consumer should be
consistent between his selected policy alternative intentions and his WS
behaviors. 

 

I am guessing that if there is push-back now, it will be because the
proposed policy processing model impinges on somebody's planned
implementation.

 

 
Received on Tuesday, 15 May 2007 02:52:24 GMT

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