Slicing Communicating Automata Specifications: Polynomial Algorithms For Model Reduction

摘要

In the industry, communicating automata specifications are mainly used in fields where the reliability requirements are high, as this formalism allow the use of powerful validation tools. Still, on large scale industrial specifications, formal methods suffer from the combinatorial explosion phenomenon. In our contribution, we suggest to try to bypass this phenomenon, in applying slicing techniques preliminarily to the targeted complex analysis. This analysis can thus be performed a posteriori on a reduced (or sliced) specification, which is potentially less exposed to combinatorial explosion. The slicing method is based on dependence relations, defined on the specification under analysis, and is mainly founded on the literature on compiler construction and program slicing. A theoretical framework is described, for static analyses of communicating automata specifications. This includes formal definitions for the aforementioned dependence relations, and for a slice of a specification with respect to a slicing criterion. Efficient algorithms are also described in detail, for calculating dependence relations and specification slices. Each of these algorithms has been shown to be polynomial, and sound and complete with respect to its respective definition. These algorithms have also been implemented in a slicing tool, named Carver, that has shown to be operational in specification debugging and understanding. The experimental results obtained in model reduction with this tool are promising, notably in the area of formal validation and verification methods, e.g. model checking, test case generation.