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Re: Revised positions for closed/open world assumptions

From: Tom Rutt <tom@coastin.com>
Date: Tue, 15 May 2007 12:38:03 -0400
To: "Rogers, Tony" <Tony.Rogers@ca.com>
Cc: Dale Moberg <dmoberg@us.axway.com>, Christopher B Ferris <chrisfer@us.ibm.com>, public-ws-policy@w3.org
Message-id: <4649E1EB.9000803@coastin.com>


I very much like this interpretation.

Tom Rutt

Rogers, Tony wrote:
> 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.
>

-- 
----------------------------------------------------
Tom Rutt	email: tom@coastin.com; trutt@us.fujitsu.com
Tel: +1 732 801 5744          Fax: +1 732 774 5133
Received on Tuesday, 15 May 2007 16:38:20 UTC

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