Specifying fault tolerance in mission critical intelligent systems

摘要

Real time intelligent systems are being increasingly used in mission critical applications in domains like military, aerospace, process control industry and medicine. Despite this vast potential, the major concern about deploying mission critical intelligent systems is their dependability. Dependability encompasses such notions as reliability, safety, security, maintainability and portability. A major concern about mission critical intelligent systems is their performance in the presence of failures. Intelligent systems are characterized by often non-existent, imprecise or rapidly changing specifications. This makes the task of characterizing an intelligent system's performance in the presence of failures much more difficult. In this paper, we characterize the failures that are likely in a mission critical intelligent system. We propose an extended I/O automata model to capture these failure specifications. We further demonstrate how these specifications can be realized in a real time expert system by structuring the knowledge base. This formalism can also be used to specify the fault tolerant properties of the underlying hardware and software over which the intelligent system resides. Thus we have an unified formalism to specify fault tolerance properties in hardware, system software and the intelligent system. This will enable us to reason about the performance of the entire system inclusive of all its components in an uniform manner.