Unification of the Models for Types, Classes and State Machines

Abstract

The static model, specified formally, and the dynamic model, represented by hierarchical state machines, are intimately related. By defining a mapping between the two, we are able to provide a definition of inheritance, multiple inheritance and behavioral subtyping for state machines based on that for formally specified types and classes, and provide a graphical representation for formal specifications in terms of state machines. The state machine notation is based on statecharts. It, however, supports both a declarative style, appropriate for types, and an imperative style, appropriate for classes. State machines may be parameterized and may be viewed from different perspectives, based on an arbitrary choice of state predicates. And states are interpreted not as an expression of concurrency, but result from a choice of independent state predicates.