Toshi, I have the following comments/observations after reviewing your wiki page... sorry I have not been able to keep a close watch on the recent activities of the group. 1. The idea of negotiation of alternatives is difficult and I think requires a better negotiation protocol. After much debate, as I recall, we limited WS-Agreement to simple acceptance of an offer. If the offer has alternatives in it, then the responder is accepting to satisfy this compound expression in any way he sees fit, with no information about how, or indeed whether his solution might vary over time and be satisfied by different clauses in the compound rules! It would take domain-specific interpretation of the SDTs to somehow fix this solution, as there is nothing in the protocol to communicate a "lowering" or simplification of the alternatives expression. (For example, I anticipated that in a basic use of JSDL for a job term, the interpretation could be defined that the service terms are chosen at job-start time and frozen, as is a typical implementation requirement for HPC resources... you would know they are not time-varying, though there is still no facility to communicate which exact parameters were chosen.) What I would suggest is that you try to keep this aspect of negotiation protocol orthogonal to the underlying notion of renegotiation. First, work on the semantics for renegotiation of an agreement as you have done, e.g. replacement/superceding of an agreement. Then, admit that basic or advanced protocols could be used to negotiate either the initial or subsequent agreement. For example, a relatively simple renegotiation could adapt the existing factory pattern for both initial and subsequent negotiations. If a future specification provides a multi-round negotiation to lower/simplify abstract agreement constraints to a more concrete solution, this could replace the basic factory pattern in both cases too. 2. I think the idea of superceding an agreement is fine, but I have trouble seeing a distinction between this and the general use of agreements in the context of other agreements. For example, the advance reservation scenario allows "claiming" of a resource reservation, and you can interpret this as adjusting an initial resource agreement to include binding to an application, with the same results as if someone simply negotiated an application with the same QoS terms in one shot... What I would point out is that this claiming/context model allows many:many derivation of agreements in the general case. E.g. I could reserve a large resource (in space-time) and consume it with multiple applications which either run serially or in parallel. I could also combine several resources (in separate agreements) into a complex application. Couldn't a renegotiation also be temporary, e.g. "boost this resource reservation for the next hour, but then fall back to the previous terms"? I am not sure how "supercededby" would be applicable here. Is it worth having one more general metalanguage for discovery/navigation of agreements which are linked to other agreements? We could use the extensibility of the wsag:Context to enumerate the actual claimed or superseded agreements, and it seems useful to have a dynamic resource property which could provide reverse-lookup of new agreements which list an agreement in the new wsag:Context too. 3. Also, a general concern I have is that the discussions are not crisp about the uses of the agreement. The talk of race conditions makes me nervous, as it seems to combine denotation of service terms with the implementation of resource managers. In my view, WS-Agreement is completely focused on the establishment of terms between the two parties, and says nothing about how one of the parties is implementing the protocol. I do not see a necessary race condition for "supercededby" because I don't think the initiator (for example) needs to be aware of this state change in order to meaningfully express a claim against an agreement. If an agreement is renegotiated, it could still be usable for claiming by name, while the actual resource manager has to take into account that there are now aliases to the newly revised delivery terms... 4. The question of having "responder initiated renegotiation" was foreseen in the optional symmetric protocol mode. In essence, if EPRs are exchanged so that both parties have an EPR representing the other party's view of the agreement, then they can switch roles and become initiator for further rounds of communication. In order to use this feature, one would need to define an extension to the protocol, e.g. have the symmetric agreement resources support an extended protocol which includes the renegotiation operations as well as the basic monitoring/cancellation operations. I think it would be appropriate to define a new negotiation protocol as a profile on this feature, so that a specific SDT would demand the presence of a renegotiation facility which would then be available as extended operations and resource properties on the Agreement resource. Again, if we consider the fuzzy case of many:many renegotiations, the best approach might be a simple RP in the agreement that holds an EPR to the renegotiation service, thereby separating discovery (via lookup of this RP an existing agreement) from claiming/context references which might involve more than one agreement at a time. karl -- Karl Czajkowski Software Architect Univa Corporation 1001 Warrenville Road, Suite 550 Lisle, IL 60532 karlcz@univa.com www.univa.com ________________________________________________________________ www.univa.com. The Leaders of Open Source Cluster and Grid Software