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Subject: high level description for CF goals/model
Based on the discussion we had at the F2F, I have tried to describe the model we were moving toward and the issues that we had not come to any resolution on. I hope I have retained the spirit of the discussion. I can take another stab at this if not, or if there is a need to take things to another level of detail. Registration WS-CAF provides a set of modular and composable service definitions to facilitate the construction of applications that combine multiple services together in Composite Applications. The fundamental capability offered by the WS-Coordination Framework specification is the ability to register a web service as a participant in some kind of domain specific function. An example scenario may be to register with a pub-sub topic to receive a stream a messages asynchronously. The registration endpoint is described by WSDL and provides operations to register and unregister for participation with specific operations described in WSDL. The semantics of the domain are communicated by a protocol identifier. While it is expected that the vast majority of protocols will involve some form of signaling to registered services via SOAP messages, this signaling is not a part of the model itself at this level. Monitoring protocols for example may express interest in participation is some interaction semantic without any subsequent signaling to registered services; Pub-sub protocols may use some optimized channel based on a native MOM protocol for message distribution. There is also no assumption how signals sent to registered services relate. Comment: note that this point, WS-Context is not referenced. Comment/Question: I am throwing out the fact that this appears to be similar to the subscription concept, but the main difference is there is no concept of expiration of the registration act. It is just "enlist/delist". An easy way to support this is to add an "isRegistered" which could be used in a number of ways. Are there other use cases to support this? How far do we want to pursue this at a conceptual level? If we opt not to pursue it, then the idea that registration, context and group membership should be considered as separate building blocks probably can't be rationalized. Group Membership WS-Context provides a late binding session model for the web services environment. SOAP messages that are to be processed within the scope of an activity contain context headers, uniquely identifying a single activity-model pair. WS-Coordination Framework extends the session model for protocols that require group membership paradigms by defining a “Registration Context”. The “Registration Context” extends the basic context type and provides a Web service reference to a “Registration” endpoint. Registration in the context of an activity adds the registered service to an activity group. Membership in the group may be used to drive some group specific protocol (eg, data replication) over the lifetime of the activity group or may be used to coordinate signals associated with a termination protocol (eg, two phase commit). The purpose and semantics of activity group membership are protocol specific. Signaling The WS-Coordination Framework currently provides generic port type declarations used to send protocol specific signals to activity group members throughout the lifecycle of the activity. Open Questions: if coordination signals are 1) defined by derivative specification and 2) also supported by specific WSDL operations in these specifications (eg, WS-TXM), are the generic coordination endpoints necessary? Do we want two ways to do the same thing (not to intermingle roles, but our position is no)? If the spec doesn't do coordination signals, does the name WS-CF make sense? Note that at the F2F we had talked about the two models (somewhat imprecisely) by referring to the generic coordination endpoint in CF as the Activity Service model and the specific operations in WS-TXM as the WS-Transaction model. Comment: Tony, I could not find the comments from Alastair that you referred to. Are they in the mail archives?
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