Dear All I would like to try and sharpen my understanding of the distinction between SOA and POA, if only because some of discussion on this seems to be somewhat too metaphysical for my taste.
I take it that everyone will agree that any business has some ordering constraints on its activities that are necessary for its operations. For instance, a Bank must "perform a credit check" before it "authorises a loan" (although, perhaps, some Banks have thrown this one out of late!!). Where there is a necessary constraint on the ordering of activities such as this, there is *necessary process*. In any real business though, there is also *contingent process*. This means an ordering of activities that reflects an arbitrary decision about practice, but has no business necessity. For instance, when I get in my car, I always "fasten my seatbelt" before I "start the engine". I could equally well do these the other way round. This leads to two possible interpretations of "SOA vs. POA": 1. The SOA view of the business is one that abstracts away the process view (both *necessary* and *contingent* process). This means that it is simply a *view* of the business and says nothing about the way the business itself (or its IT) is organised. The POA view, on the other hand, is one that focuses on the processes. 2. An SOA business is one that eliminates, as far as it can, all *contingent* process constraints from the way it conducts its activities, leaving only the *necessary* constraints. This leads to a minimum of "process" in the way the business defines and conducts its activities. A POA business, on the other hand, makes no such elimination and is therefore much more rigid. The first definition is just about views or abstractions; whereas the second is a "real" distinction in the way a business defines, implements and conducts its activities. In particular, the elimination of "contingent process" will tend to disentangle activities from their contingent process contexts so that they become "services". I take it that when people advocate "SOA over POA", they are using the second definition. Is this correct? Are there other definitions of the SOA vs. POA distinction, different from the two that I have tried to articulate above? Rgds Ashley
