“What’s a Service?” my client asked. Not what’s the technology of a service. Rather this client is starting a real Service Oriented Architecture project. Real meaning creating a new ‘application’ by creating a series of services that model granular business functions, and orchestrating those business services into business process workflows (both by BPM and by composite services) – layering on a User Interface and presto, it’s a composed application.
But they asked “what’s a service?” More specifically, what level of business functionality should become a service? A surprisingly tough question to answer , and when starting with an existing environment the answer usually is “we work with whatever level the existing applications are exposing”. Not as bad as it sounds as the existing “transactions” usually have developed over time to model that business sweet-spot – preventing the need for the architects to actually address this question.
But when starting from scratch? Many industry analysts and SOA architects have written basically “a service – we know it when we see it”. That’s a remarkably distasteful answer when speaking to a group of IT analysts or architects.
To answer this question I created the presentation below. This was round 2 for this presentation, the first edition was a complete failure (and was mostly developed by presenting language from The Open Group’s TOGAF-9). Initially I thought the failure was due to a language barrier – I presented this to a team of software architects in Israel, and while they are all fluent in English it’s not their first language. And being the presentation was heavily language based, the nuances can be difficult to grasp.
But I realized it wasn’t that. Rather, having to parse a paragraph of architecture language to try to grasp what needs to develop into a straightforward concept (within the particular business concept) just doesn’t work. So this version of the presentation attempts to simply and graphically work into the concept – how much business functionality comprises a service?
This is an original presentation, though I borrowed one small graphic from TOGAF-9’s SOA pages, and garnered some foundational ideas from a post on the same topic at the Inside Architecture blog by Nick Malik.