However, as with any new trend there are always those annoying problems that we must solve in order to offer a complete solution. In the case of SOA it’s the “last mile” issue, or bringing your SOA to your existing systems, be they built 20 years ago or 20 days ago. In other words, exposing all of your enterprise systems as services, as well as managing how those services work together.

So, how do you approach the last mile problem when building out your SOA? Simply put, it’s really a matter of understanding and applying the right technology. I recommend the following procedure:
First, create a catalog of your potential services, or existing application functions. New or old services, it does not matter.

Keep in mind that services should be limited in their scope. For instance a service that controls inventory is too broad, not granular enough. It would be much better to document all of the sub-functions and sub-sub-functions to identify 1000 potential services, not just a few out of a single enterprise application. This gives those that use the services the opportunity to mix and match services at a much lower level, and thus makes those services more useful.

Second, figure out a strategy for exposing those services. The fact of the matter each system is going to need a different technique (see above) and a different enabling technology to complete the last mile. In some instance it’s going to mean redevelopment, in other instances it’s going require software the mediates the difference between the native interfaces or standard interfaces and Web services. In some instance the Web services are already exposed, if you’re lucky.

Third, document the data and structures bound to those potential services. In other words, how does that service use data and what’s the schema employed.

Finally, you’ll need some type of strategy to test the exposed services, making sure the exposed services function and perform correctly. In some instance you need to do some tuning and tweaking, depending on what you find. Remember, these services are destined to become parts of other applications, so any quality problems will be replicated over and over again.

Clearly, integration can be complex and difficult, and the hardest part of integration is linking your existing systems to your SOA and seeing those systems as a true set of services. This is also where most IT shops fall down, not able to make the walk down that last mile. Unfortunately, it’s the last mile to your success with SOI and SOA. If you don’t complete your journey, the problem is not solved.