Service-oriented architectures (SOAs) hold a great deal of promise in standardization, scalability and cost effectiveness but their successful implementation depends upon a system definition that breaks down stove-pipes (an organizational governance issue) coupled with a clear definition of the system process layer. The importance and execution of the latter is the subject of this paper. Instead of designing the SOA from the existing services supported by enterprise IT, MBSE can be used to model the system process layer. The service needs of the enterprise can then be derived from this model. This allows the composition of the service layer to be determined by the needs of the enterprise mission/business processes. These services, when linked to the processes through the enterprise service bus then directly meet the needs of those processes. This unleashes the power of the SOA to serve the enterprise. This presentation addresses the modeling of the business processes, the derivation of the service requirements and the definition of the service layer. Attention is given to the iterative interview techniques that drive the efficient capture of accurate process models as well as the change management benefits flowing from the “front-end” ownership of the models by process owners. This ownership has been shown to facilitate the efficiency of the implementation of the SOA by minimizing the resistance to change that often impedes the introduction of the SOA to the enterprise operations.