A New Class Cohesion Criterion:

Class cohesion is considered as one of important object-oriented software attributes. Cohesion refers to the degree of the relatedness of the members in a class. High cohesion is a desirable property of classes. Several metrics have been proposed in the literature in order to measure class cohesion in object-oriented systems. They capture class cohesion in terms of connections among members within a class. The major existing class cohesion metrics are essentially based on instance variables usage criteria. It is a special and a restricted way of capturing class cohesion. Most of these metrics have been experimented and widely discussed in the literature. They do not take into account some characteristics of classes as stated in many papers. We believe that class cohesion metrics should not exclusively be based on common instance variables usage. We present, in this position paper, a new criterion, which focuses on interactions between class methods and propose a new class cohesion metric. We developed a cohesion measurement tool for Java programs and performed a case study on several systems. The selected test systems vary in size and domain. The obtained results demonstrate that our new class cohesion metric captures several pairs of related methods, which are not captured by the existing cohesion metrics. Index Terms OO Software Quality, Software Metrics, Cohesion, Criterion, Connected methods.