Object-oriented system decomposition quality

Object-oriented design is becoming very popular in today´s software development. An object-oriented information system is decomposed into subjects; each subject is decomposed into classes of objects. Good object-oriented system design should exhibit high cohesion inside subjects and low coupling among subjects. Yet, few quantitative studies of the actual use of cohesion and coupling have been conducted at the system level. These two concepts are defined qualitatively, and only at the class level, not at the system level. In this paper, metrics are introduced for cohesion and coupling and used to define a quality metric at the system level. The feasibility of the approach is demonstrated by an example using a real information system.