UML and MSC are widely used by software practitioners. SDL is an ITU standard language for telecommunications software specification. It has a formal semantics, and is supported by several commercial tools, which allow for simulation and validation of SDL design specifications as well as automatic code generation from these specifications. In order to take advantages of the SDL available tools and still use the very popular notations such as UML and MSC, we have developed an approach for specifying distributed systems in UML and MSC. MSCs are used to specify the behavior (scenarios) of the distributed system under consideration. UML, more precisely Class Diagrams and Object Diagrams, are used to specify the architecture of the system. By architecture, we mean the different components of the system and their interconnections. The MSC and UML specifications are translated automatically into a full SDL specification. In this paper, we introduce our distributed system specification style ...