Requirements for an Object-Oriented Language for the Design and Implementation of Telecommunication Systems

A telecommunication system like an ISDN network comprises a great variety of software components. It includes software for switches, the terminal equipment (like a simple telephone) but also for the management of resources and the provision of high level services like time dependent call forwarding. Software for telecommunication systems like other software must be fast, robust and easy to maintain (e.g. extensible). Like in many other application domains telecommunication software has to comply to standardized interfaces in order to enable interoperability between software of different vendors. The international standardization body ITU-T (International Telecommunication Union Telecommunication Sector) accounts for the definition of interfaces using formal description techniques. The main language to define the behaviour of telecommunication systems is SDL (Specification and Description Language). The current version SDL‘96 [Z.100] provides abstract data types, concurrency, asynchronous communication and type based definitions. The use of SDL is not confined to the standardization area. The language was successfully applied for the design and implementation of large communicating systems[PL112A]. However the language could not keep up with recent developments in the domain of distributed (telecommunication) systems (ODP [X.901], TINA-C [CM94]). The following sections motivate what language concepts are necessary for the design and implementation of telecommunication systems and how SDL fulfills these requirements.