Specifying fault tolerance in mission critical systems

Dependability is a central concern in the design of mission critical systems. A major design constraint is that the system cannot be brought down for repair during mission times. A number of alternate designs are possible for a given specification. Alternate designs necessitate evaluation. This requires capturing the system specifications and designs in the same formalism. We propose an extended I/O automata to specify fault tolerant requirements of dependable mission critical systems. The properties of the behaviors of the extended automaton can capture temporal properties like deadlines. This framework is then used to specify the fire control system of a combat vehicle and demonstrate the usefulness of the proposed framework for capturing fault tolerance aspects in mission critical systems.