>> SOA is always a tough topic to explain for first time
>> visitors.
It is not so much that it is difficult to explain, it is that there is something called Service-Orientation that is not Object-Orientation and unlike OO, SO does not fit in a single runtime (SCA kinds of attempts to do that). SO is by definition, distributed, architected, hence the need to express SO outside any specific runtime. Model Driven SOA is SOA, there is simply no other way.