RE: [soa-rm-ra] SOA-Pro & Core Concepts

[michael.poulin@uk.fid-intl.com]

Line 2104:
Choreograpy
A technique used to characterize and to compose service-oriented
business collaborations based on ordered message exchnges between peer
entities in order to achieve a common business goal.


I used to think about Choreograpy [actually, ChoreograpHy], as of a low level protocol for collaboration between entities. For SOA services, Choreography is direct collaboration between services. However, I do not think that service consumer has to inform service provider about how the service will be used (unless there is a policy requirement) via the service contract.

Explicit knowledge of one service about another service leads to violation of SO principle of Autonomy: service has to be self-contained entity capable of providing offered business functionality and RWE by itself. 

If Autonomy is the axiom, then what a service might need another service for? An answer may be  for an external task, which requires a composition of services. How a service may guess what the task might be and which service it needs to deal with according to the task? There is no way to know this.

All said only means that a service and all its own attributes may not know anything about Choreography and/or Orchestration; both of them should be EXTERNAL means with regard to the service. Am I wrong? 

In the Figure 21 - Service Interface Model - the Process Model as well as Event Model may not be attributes of service interface. There are no events in the interface (if I am wrong, please, give me an example), plus, only process model related to the interface is the model of message exchange like request-only, request-response, etc. This model has nothing to do with Choreography or Orchestration but the latter can use the model. 

Presence of Choreography or Orchestration inside Process Model of the interface is very confusing to me. If something needs a service to participate in Choreography or Orchestration, this must be totally transparent to the service itself, I believe.

- Michael