Colin, I agree that creating business meaningful services is of utmost importance, and that the big picture is the most important one.
But, you can have several layers of business meaningful services - all coarse grained in one way or another (e.g. focused on a process or some kind of information). And, if you only care about the biggest picture you are bound to run into a lot of trouble. That sounds more like powerpoint, ivory tower architecture to me. Caring about architecture at a somewhat more detailed level does not mean that you do not care about the big picture - at least not in my world. /Herbjörn 2009/4/15 Colin Jack <[email protected]> > > > > > I do not understand, why bother with services? Make them RPC, and > > end the story. > > > > I think that both Erl & Herbjör miss the point - why services, > > especially business services are coarse-grained. They are such > > because they implement business functionality. Retrieving a data > > field content from a database that somebody calls 'business data' - > > fine-grained activity - has nothing to do with any business > > functionality, this is why I do not consider it as a business > > service (in spite of calculation capabilities of modern hardware). > > I agree, discussions with people from the business are not at this low > level nor should they be. This is one of the many reasons I dislike the > style of SOA Erl focusses on so much in his books (others include the > unnecessary complexity and, as I see it, inelegance of the resulting > solutions). > > The linked pattern decompose capability ( > http://www.soapatterns.org/decomposed_capability.asp) is a good example of > focussing on the details. In the example Invoice service has ReportProcessed > which is moved to the InvoiceHistory service. Maybe there is an argument for > that change, for example even if we went for a RESTful approach we might > decide to create more fine-grained resources so instead of a PUT to Invoice > to change the Process value we instead POST an InvoiceHistoryEvent. > > Whilst these sorts of choices are important I think if we only focus on > decisions at this detailed level we do miss the bigger picture (business > services, capabilities or bounded contexts depending on your viewpoint). > > Colin > > > -- Med vänliga hälsningar Herbjörn Wilhelmsen
