A Redefinition Metric for Object-Oriented Systems

Although the inheritance mechanism is one of the key points for the extendibility and reusability aspects of object-oriented (OO) systems, its current use has illustrated that the introduction of conceptual inconsistencies is possible in a class hierarchy. This paper discusses the issues involved in measuring aspects of redefinition of methods in an OO model. The work is intended to raise the problem of considering measures of redefinition as a metric for the OO paradigm. Also, practical experiments on Smalltalk libraries or applications will demonstrate that the results obtained allow the detection of potential inheritance design flaws. It is shown how the redefinition metrics (and variants), together with current existing metrics form a complementary measurement technique for detecting inheritance anomalies. Thus, an approach to assess the level of "goodness or badness" in OO design. Finally, our aim is to provide a clear understanding of the use of inheritance in the OO paradigm and investigate potential new metrics so as to measure and analyse their impact on design.