The numerous design specifications in the service-oriented architecture (SOA) standard space reflects knowledge captured from the various perspectives. However, most of these approaches merely exhibit any compliance with service design facets described in reference architectures. Moreover, majority of this approach lacks correspondence between the business process facets to service design facets and its real-world effects. This leads to semantic gap between services representation, its association with the business processes, and invocation of services to its real-world effects. In this paper a formal model of service-oriented system (SOS) is proposed. The SOS is divided into information model, process model and action model. The semantic relationship between these models helps in reducing the gap between the business processes and services, as well as services to its real-world effect. Further, the proposed service model facilitates flexible, reusable and scalable service composition and it follows the open reference standards of SOA.