Advanced Topics on SDL and MSC

This issue of Computer Networks is dedicated to advanced topics on the Specification and Description Ž . Language SDL and Message Sequence Charts Ž . MSC . It is based on the tutorials presented at the 8th SDL Forum held at the Institut National des Ž . Telecommunications INT , Evry, France, September ́ ́ 22–26, 1997. This Forum was organized by the INT in collaboration with the Centre National d’Etudes des Ž . Telecommunications CNET . INT is an engineering ́ ́ telecommunication school and leader in the teaching of the SDL language, and in research on test generation methods from SDL specifications. CNET is the research center of France Telecom. SDL is largely used by their engineers in different domains; such as, protocol engineering and test generation methods from SDL specifications, and, especially, in the area of ISDN systems, ATM networks, Intelligent Networks and mobile communication. These contributions have helped the introduction and use of SDL technology in industry. The SDL and MSC user communities are composed of many different groups with very different interests concerning these languages. These communities are basically: Ø academics and students with a strong inclination for improving theory, Ø researchers involved in standardization bodies looking for ‘friendly’ modeling facilities in the languages and tools, and Ø manufacturers looking for an efficient design methodology encompassing the entire software life-cycle. The SDL Forum brings these communities together, and, thus, the tutorials take into consideration different levels of knowledge and fields of interest. The advanced topics presented in this special issue have been targeted on four specific areas: language semantics, performance evaluation, and validation and testing. They have been presented by specialists, of which only two are not directly involved in the ITU-TrSG10 standardization work. Message Sequence Charts is often used as a complementary formalism to SDL. It describes the interactions between the system entities and has become an essential tool for software design. The definition of a formal semantics for this language is a significant topic. Sjouke Mauw and Michel A. Reniers have focused their paper on this important subject and propose an operational semantics for MSC’96. Andreas Mitschele-Thiel and Bruno Muller-Clos̈ termann address, in their paper, the issues related to the performance of systems specified with SDL and MSC. They also introduce some basic performance modeling techniques and survey approaches that integrate performance evaluation into the context of SDL and MSC. Service validation has become a costly and complex task. This is mainly due to the fact that telecommunication services tend to be more and more com-