Based on the ITU-T Recommendation Z.100 [27]---also known as SDL-92--- we define a formal semantic model of the dynamic properties of Basic SDL in terms of an abstract SDL machine. More precisely, we use the concept of multi-agent realtime ASM [17] as a semantic platform on top of which we construct our mathematical description. The resulting interpretation model is not only mathematically precise but also reflects the common understanding of SDL in a direct and intuitive manner; it provides a concise and understandable representation of the complete dynamic semantics of Basic SDL. Moreover, the model can easily be extended and modified---a particularly important issue for an evolving technical standard. In this article, we consider all relevant aspects concerning the behavior of channels, processes and timers with respect to signal transfer operations and timer operations. The model we obtain is intended as a basis for formal documentation as well as for executable high-level SDL specifications.

SDL, Basic SDL, Semantic Foundations, Telecommunication Systems, Formal Documentation, Executable Specifications, Abstract State Machines