Toward a unified approach to coupling

We describe a unified approach to coupling that incorporates four disparate elements, namely, taxonomies for classical coupling; taxonomies for object-oriented coupling; metrics for classical coupling; and metrics for object-oriented coupling. A single instance of coupling between two modules (or classes) can incorporate several points of dependency between the two modules (or classes). It is the combination of the effects of these dependencies that gives the true measure of that instance of coupling. We identify a metric based on three types of dependencies that commonly exist between modules, namely, referential dependency, a measure of the extent to which the program relies on its declarations remaining unchanged; structural dependency, a measure of the extent to which the program relies upon its internal organization remaining unchanged; and data integrity dependency, a measure of the vulnerability of data elements in one module to change by other modules. We show how this approach can be used to describe different forms of coupling. We also compare our metric with another coupling metrics.