Specifying and Analyzing System Level Inter-Component Interfaces

Abstract

In control systems, the interfaces between software and its embedding environment are a major source of costly errors. For example, Lutz 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.

In this paper we discuss a formal approach to the specification and analysis of inter-component communication using a revised version of RSML (Requirements State Machine Language). The formalism allows rigorous specification of the physical aspects of the inter-component communication and forces encapsulation of communication related properties in well defined and easy to read interface specifications. This enables us to both analyze a system design to detect incompatibilities between connected components and use the interface specifications as safety kernels to enforce safety constraints.