Towards a New Formal SDL Semantics

R. Gotzhein, B. Geppert, F. Rößler, P. Schaible

in: Y. Lahav, A. Wolisz, J. Fischer, E. Holz (Eds.), Proceedings of the 1st Workshop of the SDL Forum Society on SDL and MSC, SAM98, Berlin, 1998


In 1988, a formal semantics for SDL has been added as Annex F to the Z.100 SDL standard [5,6,7,8]. Along with the efforts to improve SDL, the semantics has been revised several times since then. To understand the semantics, intimate knowledge of the language Meta IV is required. Meta IV is a formal language based on synchronous communication between a set of concurrent processes. Essentially, Annex F defines a sequence of Meta IV programs that take an SDL specification as input, determine the correctness of its static semantics, perform a number of transformations to replace several language constructs, and interpret the specification. It has been argued that this style of defining the formal semantics is particularly suitable for tool builders. With the ongoing work to improve SDL, and a new version called SDL- 2000 to pass the standardization bodies shortly, it has become apparent that a decision concerning the SDL semantics needs to be taken. One alternative is to revise the existing SDL semantics, which has the advantage of continuity. Another alternative currently under consideration is to redo the SDL semantics, which offers an opportunity for improvement. In this paper, some of the choices that go along with a new definition of a formal SDL semantics are presented and discussed. Based on the results of this discussion, a coarse outline for a new formal semantics is proposed.


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