Hi all, based on Toshi's slides and the discussion I prepared three pngs with the scenarios I see: AI = MI AR = MI (rendered with the pending agreement as proposed by Karl) AR = MI ( 2PC as proposed by Toshi) Anything else we should consider? Best regards Wolfgang Karl Czajkowski schrieb/wrote:
On Mar 01, Toshiyuki Nakata modulated: ...
A better rendering might eliminate this round-trip. What you could do is send a PendingAgreement EPR in the initial renegotiation offer, so the renegotiation responder already has an EPR before he decides to accept. This would also support the Accept message, so the responder could simply invoke that and be done with it.
WOuld this be same for both the cases of MI=AI and MI=AR?
Yes, this symmetric rendering is general. The asymmetric client-server case is just a subset where the "optional" initiator-provided Agreement EPR is absent, so no endpoint is known for initiating new web service requests towards the agreement initiator. As such, this purely client-server subset is not suitable for MI=AR, unless you want to use some more passive means of deliverying offers, e.g. via resource properties or notification, but it is perhaps simpler for basic MI=AI cases.
We were discussing in the group about the appplicability of having a modified EPR for MI=AR case...
For the symmetric case, it is important to understand that there are already TWO EPRs for the underlying agreement. Each party presents a web resource representing his own view of the agreement. The symmetry was made optional because people wanted WS-Agreement to be usable in purely client-server environments, even if it lacked some of the general capability. Conceptually, the initiator's pending agreement always exists when he makes an offer, but the specification allows him to omit the EPR for this implied pending agreement if he doesn't care to support symmetric message patterns.
So, renegotiation would generate two more EPRs when it is done. The initiator can provide an EPR to the pending offer and the responder has to produce an EPR if he accepts (or if he may accept in the async case). These two renegotiation EPRs represent each party's view of the distributed decision process that supercedes the agreement represented in the original two agreement EPRs.
In the symmetric case, there is probably a desire to use another name space for the agreements so that both parties' agreement resources can be easily correlated by seeing that they share the same agreement ID, despite having separate agreement EPRs. This is an existing issue regardless of whether you intend to do renegotiation.
karl
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