Equivalence in LOTOS and its decision method

This paper considers the specification described in LOTOS, which is the formal description language for the communication system. A decision method is proposed for the equivalence between two arbitrary systems (between definition of service and the protocol specifications, for example). In this paper, based on the definition of the weak bisimulation equivalence, which is the definition of equivalence in LOTOS, the concepts of the k-weak bisimulation equivalence and the canonical 1-weak bisimulation are introduced. It is shown that those concepts are mutually necessary and sufficient. Then, based on the canonical 1-weak bisimulation equivalence, the decision algorithm is presented for the weak bisimulation equivalence between two LOTOS specifications with finite states by the same method as in the equivalence class partitioning of the equivalent states in a finite automaton. The traditional decision of the equivalence using the transformation by algebraic rules is heuristic and often does not succeed in the decision. By contrast, the proposed method has a merit in that it is always applicable to the system with finite states.