Abstract
This paper proposes a comprehensive suite of measures to quantify the level of class coupling during the design of object-oriented systems. This suite takes into account the different OO design mechanisms provided by the C++ language (e.g., friendship between classes, specialization, and aggregation) but it can be tailored to other OO languages. The different measures in our suite thus reflect different hypotheses about the different mechanisms of coupling in OO systems. Based on actual project defect data, the hypotheses underlying our coupling measures are empirically validated by analyzing their relationship with the probability of fault detection across classes. The results demonstrate that some of these coupling measures may be useful early quality indicators of the design of OO systems. These measures are conceptually different from the OO design measures defined by Chidamber and Kemerer; in addition, our data suggests that they are complementary quality indicators.