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Subject: Re: [ws-tx] Issue 045 - WS-AT: Meaning of "wsp:Optional"
>malhotra: Although WS-Policy does not define the semantics of missing assertions, it is not >unreasonable to assume that if a particular policy assertion does not appear, it means >"don't do that". For example, if an endpoint does not have a Reliable Messaging >assertion in its policy it's fair to assume that it does not want a reliable protocol >used. And if there is no encryption assertion, this seems to imply that messages >shd not be encrypted. > >But there are some tricky areas. For example, if there is no encoding assertion does >this mean that no encoding shd be used? It seems to depend on whether the absent >assertion is among the set of 'known assertions'. > >In any case, I think WS-TX is free to adopt the absence-means-don't-do-it semantic >but it would be good if this was spelt out clearly in the spec. > >All the best, Ashok > mm1: This statement from WS-Policy actually does give guidance around missing policy assertions, Ashok (as previously stated). (1) In Section 3.2 of WS-Policy: ..."An assertion whose type is part of the policy's vocabulary but is not included in an alternative is explicitly prohibited by the alternative." Interpretation of the above WS-Policy text indicates that the WS-AT description of the compact shortcut, wsp:Optional="true", has to be the policy alternatives "MUST" and "MUST NOT" rather than the current specified alternatives of "MUST" and "SHOULD NOT". Otherwise, WS-AT is misusing WS-Policy.... We should consider both client and server side behavior. For example, what happens when the server doesn't recognize the transaction? There is a need to clarify and be explicit here. Thanks. >>(1) In Section 3.2 of WS-Policy [reference 2]: >> >>"An assertion whose type is part of the policy's vocabulary >>but is not included in an alternative is explicitly >>prohibited by the alternative." >> >>Interpretation of the above WS-Policy text indicates that the >>WS-AT description of the compact shortcut, >>wsp:Optional="true", has to be the policy alternatives "MUST" >>and "MUST NOT" rather than the current specified alternatives >>of "MUST" and "SHOULD NOT". Otherwise, WS-AT is misusing WS-Policy. >>
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