Interpreter in SOA

I am hearing lots on "Semantics" in SOA. I could imagine this make more sense if we build an application from the foundation. But usually this is not the case in enterprise world. Most of the organization who are in the verse of using SOA for their upcoming solutions, already having some kind of legacy or semi-legacy application running. Most of these SOA application going to integrate with this legacy application at long run. So how we are going to make a Semantic integration with this application as legacy application works in different manner. Thats hints to title of my topic ie. we need an interpreter for our SOA application which will talk to semantic based integration in one hand and other hand it will understand the customized language. I am finding a great void there and need to address this along with our semantic initiatives.