The provision of efficient methods and tool support for the development and engineering of distributed systems is a key enabling factor for the evolution of Information Technology. Distributed as well as telecommunication systems consist of components which are distributed across networks and have to cope with concurrency, autonomy, synchronization, and communication issues. The development of correct and efficient distributed systems is a complex and complicated task. CASE tools support the design and partially the validation of distributed systems in the modelling phase. KEYWORDS Languages, Object Oriented Implementation, Model Combination, Meta-Modelling, UML, SDL