Measuring Indirect Coupling

There is an increasing awareness on the importance of software measurement within the software engineering community, as well as the necessity of respecting the scientific basis of measurement. However there is little evidence for the latter as there is a tendency for researchers and practitioners to apply software metrics without a full awareness of what they mean. Coupling, which is the measure of the interdependence between parts of a software system (e.g. classes), is one important property for which many metrics have been defined. While it is widely agreed that there is a relationship between high coupling and poor maintainability, I argue that current empirical evidence toward this is insufficient to promote a full understanding of this relationship. Part of this is due to the lack of coverage of all forms of connections that comprise coupling. To illustrate this I identify a specific, indirect, form of coupling that manifests between two seemingly unrelated parts of the system through hidden connections. My thesis is that there is a relationship between indirect coupling and maintainability. To gather evidence for this I follow a methodology based on the philosophies of key software metrics researchers. This involves operationally defining indirect coupling so that it can be accurately measured, establishing an explanatory model as to the relationship between indirect coupling and maintainability, and finally empirically corroborating this model.