I was talking SOA – again! I was arguing that modeling of services in UML, BPEL, and any other fancy acronym immediately constrains you to a specific implementation. For example, UML means that your are thinking OO already, BPEL means that your are thinking business processes already. But are those (and others) the best ways to model or represent a service?
In SOA, I have a suspicion (as yet untested!) that a service is closer to an intention than anything else that I can think of because it describes the latent value of the business that invariably is lost by SOA implementations and product stacks. Now that leaves us with a problem – how do you describe intentions consistently across any domain? I don’t know how to do this because to describe intentions in a domain, you need to understand the vocabulary of the domain. Until we can represent vocabularies then only can we create a metamodel for these business intentions.
So how do we model intentions in a single domain since I cannot use UML (implementation!), XPDL (implementation!), BPEL (implementation!) etc? Since the domain is constrained by its vocabulary, we need to create a language that uses this vocabulary. And that, my dear folks, is nothing but a DSL. If we, therefore, model intentions (the services) with a DSL, then we are in a position to translate or transform that intention into any implementation that we like. Realistically, we will likely need additional metadata surrounding the intention described in the DSL to satisfy UML, XPDL, BPEL, WSDL, RESTful APIs, etc.
When we think of the business as what they intend to do or achieve, then we are actually working at a higher level of abstraction – at a meta-level. That is hard to do, but if you do it reasonably well, then you have more freedom when it comes to implementation.
SOA is so screwed up at the moment and most are climbing into or out of rabbit holes because the business intentions are being ignored or forgotten far too early or thought about far too late. Perhaps the most effective SOA implementations will be realised with a suite of DSL’s and the only toolset that you really need is a language workbench and some very skilled language oriented programmers.