416 ◾ Software Metrics
9.4.1 Measuring Coupling in Object-Oriented Systems
Briand, Daly, and Wüst developed a framework for the measurement and
analysis of coupling in object-oriented systems (Briand et al. 1999b). e
framework supports a variety of perspectives on the notion of coupling,
as well as mechanisms that couple object-oriented entities. Many object-
oriented connections tend to be persistent—the connected entities can
remain connected between method invocations, and may persist over
the lifetime of an object. Persistent connections include objects coupled
through associations that are implemented using instance or state vari-
ables. Generalization/specialization relations that are implemented using
inheritance are persistent