A classical view of object-oriented cohesion and coupling

AARON B. BINKLEY AND STEPHEN R. SCHACH Computer Science Department, Vanderbilt University, Box 1679, Station B, Nashville, TN 37235, USA. __________________________________________________________________ Contact: Stephen R. Schach Computer Science Department, Vanderbilt University Box 1679, Station B, Nashville, TN 37235 ☎ 615/322-2924 Fax 615/343-5459 E-mail: [email protected] __________________________________________________________________ The cohesion of a class or object is equivalent to the cohesion of a module; that is, it can be expressed in terms of the cohesion of a module at an equivalent level of abstraction. Similarly, the coupling between classes and objects always corresponds to classical (module-based) coupling. It is therefore a source of confusion to refer to object-oriented cohesion or object-oriented coupling. These results are then extended to object-oriented metrics in general. For a metric to be strictly object-oriented, it is necessary for that metric to be inheritance-related. But inheritance, though necessary, is not sufficient; for example, coupling in the object-oriented paradigm can be induced by inheritance, but is nevertheless always equivalent to coupling as it is found in the module-based (classical) paradigm.