On the Behavior of Complex Object-Oriented Systems

Over the years, the main approaches to high-level system modeling have been structured-analysis and object-orientation (OO). The two are about a decade apart in initial concep-tion and evolution. SA started out in the late 1970’s by De Marco, Yourdon and others, and is based on “lifted ” classical procedural programming concepts up to the modeling level and using diagrams [CY79]. The result calls for modeling system structure by func-tional decomposition and the flow of information, depicted by hierarchical data-flow di-agrams. As to system behavior, the mid 1980’s saw several methodology teams (such as Ward/Mellor [WM85], Hatley/Pribhai [HP87] and our own Statemate team [HHN90]) making detailed recommendations enriching the basic SA model with means for capturing behavior based on state diagrams, or the richer language of statecharts [Har87]. A state diagram or statechart is associated with each function to describe its behavior. Carefully defined behavioral modeling, we should add, is especially crucial for embedded, reactive, and real-time systems. A detailed description of the way this is done in the SA framework appears in [HM98]. The first tool to enable model executability and code synthesis of high-level models was Statemate, made commercially available in 1987 (see [HHN90], [Inc])