Developing dependable real-time systems

A growing number of safety-critical systems is controlled by computer systems. In the context of several research projects solutions were suggested how to reduce the implementation effort for dependable real-time systems. Unfortunately most of these approaches are based on special hardware solutions or restricted to specific application domains. In addition most of the application realize only fault-tolerance concerning communication errors, whereas fault-tolerance at application level is left to the developer. Within the Zerberus project a development process is suggested that is not restricted to a special kind of hardware, operating system or programming language. The main idea of Zerberus is the separation of the application functionality from the fault-tolerance mechanisms. The fault-tolerance mechanisms are then generated automatically by the Zerberus code generator. As basis for this generation a high-level platform independent description of the application provided by the developer is used. This so called functional model describes the application tasks, the interaction between these tasks, the timing constraints and the input and output of the system and can be specified by using the Zerberus language. Due to the automatic code generation of the fault-tolerance mechanisms the implementation effort is restricted to the absolute application dependent code. The automatic generation of the FT-mechanisms is based on preimple-mented, application-independent templates that are adopted to the application during the code generation process. Templates are currently offered for the operating system VxWorks 5.5 and the programming languages C and C++.