Object-oriented specification of reactive systems

A novel approach to the operational specification of concurrent systems that leads to an object-oriented specification language is presented. In contrast to object-oriented programming languages, objects are structured as hierarchical state-transition systems, methods of individual objects are replaced by roles in cooperative multiobject actions whereby explicit mechanisms for process communication are avoided, and a simple nondeterministic execution model that requires no explicit invocation of actions is introduced. The approach has a formal basis, and it emphasizes structured derivation of specifications. Top-down and bottom-up methodologies are reflected in two variants of inheritance. The former captures the methodology of designing distributed systems by superimposition; the latter is suited to the specification of reusable modules