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Issue No. 06 - June (1993 vol. 19)
ISSN: 0098-5589
pp: 554-570
<p>It is shown how a probabilistic dependability model of a safety-critical system can be derived from a trace-based functional model of the system. The functional model is a communicating sequential process (CSP) that includes command, failure, and repair events. The dependability model is a time homogeneous Markov process with transitions determined by these events. The method applies to deterministic systems that can be described in terms of a finite number of states and in which all event occurrences are stochastic with exponential time distribution. The derivation is carried out in two steps. An algorithmic determination is made of a finite automaton from the specification of the CSP process. The automaton is transformed into a Markov process. The Markov model for this system is used to determine the waiting time to terminal failure. The theory is applied to a larger and more realistic example: a gas burner system operating in the on-off mode. For this system, the waiting time to terminal failure is calculated, and the number of failures per year in a large population of identical, independently operated systems is estimated.</p>
probabilistic dependability model; safety-critical system; trace-based functional model; communicating sequential process; time homogeneous Markov process; deterministic systems; event occurrences; stochastic; exponential time distribution; finite automaton; specification; waiting time; terminal failure; gas burner system; communicating sequential processes; fault tolerant computing; finite automata; Markov processes

J. Nordahl, M. Hansen and E. Sorensen, "From CSP Models to Markov Models," in IEEE Transactions on Software Engineering, vol. 19, no. , pp. 554-570, 1993.
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