SOA - where do I start?

I have just read a paper from IBM about predicting and measuring SOA projects ROI's. I'm not impressed. Urging people to be satisfied with instinct and hope is not going to fly with any CFO's I know. IBM's approach is flawed from the outset in that it fails to capitalise on, or at least preserve, the investment companies have made in their existing IT infrastructure

Very few of us are going to be able to begin with a greenfield site. The reality is that we start with a host of legacy systems, all of which were conceived long before Service Oriented Architectures were invented. Very wealthy companies with a history of being early adopters can afford to set up large teams and set them the task of re-creating their primary systems as collections of re-usable services. Most of us cannot. Nor do I believe that you should even if you could.

A better way is to identify quick kills and make a difference early. For example, re-designing your interface to your principal customer or supplier might be a good place to start. The questions is how? You still have that legacy ERP system to deal with.

The answer is to add a software component to your IT infrastructure I call an ASM - Application Service manager. It's function is to integrate closely with your ERP system and loosely with everything else. Each ASM should be designed to expose a specific function within your existing ERP system as a service. To get going with a project to allow major customers to place orders directly via a web service, you only need one ASM. Building an ASM, if you use the right tools, will take less than a man week, maybe much less, depending on your ERP system.

Once you have built one, move on to another - maybe to upgrade your supplier relationships this time. Pretty soon, you will have exposed a significant number of functions from within your existing ERP system as services. Along the way, you can introduce new functionality made up entirely of elemental services and create improved processes made up of services exposed via ASM's and new services composed from new elemental services.

Each step of the way you will have made a real, measurable difference. Users will see the benefits quickly and support the process. management will see a return and the ROI will be tangible.