Specification and analysis of system level inter-component communication

In embedded systems the interfaces between software and its embedding environment are a major source of costly errors. For example, R.R. Lutz (1993) reported that 20%-35% of the safety related errors discovered during integration and system testing of two spacecraft were related to the interfaces between the software and the embedding hardware. Also, the software's operating environment is likely to change over time further complicating the issues related to system level inter component communication. We discuss a formal approach to the specification and analysis of inter component communication using a revised version of the RSML (Requirements State Machine Language) specification language. The formalism allows rigorous specification of the physical aspects of the inter component communication and enables encapsulation of communication related properties in well defined interface specifications. This allows us to both analyze a system design and detect incompatibilities between connected components and use the interface specifications as simple safety kernels to enforce safety and sample liveness constraints.