Thank you, Colin, for 'stoling', it is very much expected. As of 'Anyhow I certainly think a business service should define the context for one or more domain models, or thats the way I see things at least' would say that I understand in the opposire order. That is, the business model separated per domain, defines the context where the service operates (accessed and executed). An execution context is the external constraint to the serivce and, respectively, to the domain dirven object design within the service body (realisation).
- Michael ________________________________ From: Colin Jack <[email protected]> To: [email protected] Sent: Monday, April 20, 2009 1:41:06 PM Subject: [service-orientated-architecture] Re: Joe on Microsoft's combination of SOA & Storage > From my last conversation with Eric Evans, I did not get an > impression that business service and context in DDD are the same. > In DOSOM, business service defines the scope, not the context, of > domain object modelling, leaving the execution context outside of > the service. This allows reuse of the service in different > execution contexts. I've got the DOSOM stuff in my list of things to read so this reply doesn't relate to it specifically. It is also possible we're talking at cross purposes, we could have different interpretations of terms like "business service" and context. In this conversation what I'm saying is that I believe Evans is correct when he says: "Explicitly define the context within which a model applies. Explicitly set boundaries in terms of team organization, usage with specific parts of the application, and physical manifestations such as codebases and database schemas. Keep the model strictly consistent within those bounds, but don't be distracted or confused by issues outside." Thats in the chapter on the BOUNDED CONTEXT pattern. Anyhow I certainly think a business service should define the context for one or more domain models, or thats the way I see things at least. However I don't really mean execution context here, but to make sure I was using the definition of execution context you were meaning I stole it from your blog (http://www.ebizq. net/blogs/ service_oriented /2009/02/ so_principle_ of_service_ execution_ context.php). You point out OASIS define it as: 'the set of technical and business elements that form a path between those with needs and those with capabilities' ..and.. '... the execution context is also the context in which the interpretation of data that is exchanged takes place. A particular string has a particular meaning in a service interaction in a particular context - the execution context'. So for me the first definition doesn't really offer us much in the context of domain models, but the second is more relevant. - Colin
