INTRODUCING OBJECTCHARTS OR HOW TO USE STATECHARTS IN OBJECT-ORIENTED DESIGN

Object-oriented design is a software development method which is carried out in a bottom up fashion. Recently, much work has been done on providing notations to support top-down design and architectural descriptions. This paper introduces such a notation called "Objectcharts" for specifying object classes. An Objectchart diagram is an extended form of a Statechart, which characterizes the behavior of a class as a state machine. The Objectchart transitions correspond to the state-changing methods that the class provides and those that it requires of other classes. Object attributes and observer methods annotate Objectchart states. Firing and postconditions are used to specify the effect of transitions on class attributes. The Objectchart notation is described through the development of an Alarm Clock application. The paper shows how Objectcharts can be used to find subtyping inheritance relationships between classes, and concludes with a description of a systematic approach for evolving Objectchart specifications.