TRUE or FALSE : SOA cannot be implemented without WebServices?

If you are ready with your answer, hold on to it…. Lets validate towards the end of this note.

Last week I met with couple of my customer architects in one of the technology roadshows. When one of the researchers mentioned that SOA is much broader than a technology concept and WebServices is just one of the technology enablers, a customer architect got agitated and argued vehemently against these notions. He later summed up in an email : "my only point is that if we decide that SOA is not about technology or webservices etc, then perhaps this topic should be discussed somewhere else (not between architects and researchers) .. I apologize if I wasn’t clear." This quasi confrontation, which I think is a healthy one, triggered some thoughts in my mind the result of which is the above quiz.

Here are my thoughts …. Before going into details below, lets keep one thing in mind loud and clear: SOA (Services Oriented Architecture) is about "Sharing of Services". It’s about reusability, repeatability, and maintainability!

WebServices are NOT essential to implement SOA: if you operate in a homogenous environment. Here's my explanation ...

Most of us techies, that work on OOAD principles Java/J2EE, C++ or .NET, can clearly visualize what I am talking about. If not, here's an example: when you write code, don’t you organize repeated calls to a specific algorithm to a separate function or a method?

Now expand the thought further. While developing a comprehensive application, you must have used common exception handling and security services across multiple different modules. Do you agree that's a shared-services approach?

Now, broaden that same thought to multiple applications in an environment that is pure J2EE. Cant one application communicate with other application to leverage some of its "services". Lets take a specific example - lets consider two different applications

Application 1 - Part Inventory System written in J2EE that has a method to query the database for available inventory.

Application 2 - Spare Parts Management system under development in J2EE, requires inventory information. In this scenario, cant we leverage the query function along with the data available in Application1? So, aren't we using the shared services approach?

In the scenarios described above, reusability, repeatability and manageability led to shared-services approach which I think is the foundation of Service Oriented Approach. In my mind, service oriented thought process started and proliferated when client-server computing emerged. Later when distributed computing gained pace, much more clarity got added to service oriented thinking through shared-services approach.

The key constraint here is that we operated in a homogenous environment! When you operate within a homogeneous environment where visibility among systems is not an issue, (same OS, networking infrastructure, common communication protocol etc), two disparate application can "share-their-services"

WebServices ARE essential to implement SOA: if the environment changes to a heterogeneous one, then YES.

So, where do we use WebServices? In a heterogeneous environment that requires two different technology stacks to interoperate or where there is no visibility among systems due to enterprise boundaries. A simple example of heterogeneous environment: J2EE and .NET. An example for no-visibility situations: two J2EE systems at different enterprises that are business partners that agree to share information. Here WebServices with the concept of service-provider, service-consumer and service-directory comes into play.

To conclude, WebServices are NOT essential if SOA is thought in a visible-homogeneous environment. But, WebServices are essential in a heterogeneous technology platforms or inter-enterprise environments.

So, the answer to my question: Neither true nor false.

What do you all think?