A Pattern Language of Statecharts
Sherif M. Yacoub; Hany H. Ammar
Computer Science and Electrical Engineering Department
West Virginia University, Morgantown
West Virginia, WV26506
Introduction
Finite state machines and their extension to statecharts are widely used in reactive systems. David Harel [Harel87] has introduced statecharts as an extension of finite state machines to describe the complex behavior of an entity. The formalized concepts of statecharts and their specifications have been used in many applications. Here, we show how to solve recurring design problems in implementing statechart specification of an entity in an object oriented application. The statecharts' patterns represent solutions to frequent design problems that are commonly thought of by system designers, which include how to deploy hierarchy, orthogonality, and broadcasting in a statechart's object oriented design. Since statecharts are frequently applicable to software applications, thus it is helpful for the system designer to directly exercise the statechart pattern language in his application design.
In the next section, a quick background of statechart is presented, then a pattern map summarizes the statechart patterns and their relation to finite state machine patterns. The rest of the sections describe the patterns themselves.