Requirements specification and analysis of fault-tolerant digital systems

We present an integrated computer-aided design environment, the PrT (predicate/transition) net system, in order to systematically introduce fault-tolerant properties into the design of complicated digital systems. This is accomplished by exploiting a formal specification of the system requirements in which the amount of necessary redundancy can be determined. The system is based on an integration of PrT nets with regular expressions. PrT nets are used to describe and analyze a high level system and regular expressions are used to describe and analyze the more detailed system structures. Both models provide us with well-defined levels of fault diagnosis needed in the digital system design. An S-invariant technique can be used to check the constancy of PrT nets; and a finite state automaton can be used to check the acceptability of regular expressions. Furthermore, the regular expression can also enable a system designer to determine redundancy in order to perform error correction. In consequence, our approach is superior to the current techniques for requirements analysis. Finally, main results are presented in the form of four propositions and supported by some experiments.