On the dependability design of manufacturing information systems

In computer integrated manufacturing environments, dependability is a crucial attribute for the production management and control information system, which should be carefully assessed during system design. This paper discusses a global approach for assessment of the dependability of industrial information systems, covering all the phases of a study, from initial system modeling to dependability analysis and evaluation. After the presentation of the modeling concepts and tools, the paper focuses on the dependability evaluation. Two complementary algorithms are discussed, one based on the device stage method and the other on the automatic derivation of analytical expressions for the state probabilities and their symbolic evaluation. The central feature of these algorithms is their ability to deal with nonexponential stochastic processes, a fundamental requirement for this class of systems.