ABSTRACT

Reuse and reusability are two major aspects in object oriented software which can be measured from inheritance hierarchy. Reusability is the prerequisite of reuse but both may or may not be measured using same metric. This paper characterizes metrics of reuse and reusability in Object Oriented Software Development (OOSD). Reuse metrics compute the extent to which classes have been reused and reusability metrics computes the extent to which classes can be reused. In this paper five new metrics namely- Breadth of Inheritance Tree (BIT), Method Reuse Per Inheritance Relation (MRPIR), Attribute Reuse Per Inheritance Relation (ARPIR), Generality of Class (GC) and Reuse Probability (RP) have been proposed. These metrics help to evaluate reuse and reusability of object oriented software. Four extensively validated existing object oriented metrics, namely- Depth of Inheritance Tree (DIT), Number of Children (NOC), Method Inheritance Factor (MIF) and Attribute Inheritance Factor (AIF) have been selected and investigated for comparison with proposed metrics. All metrics can be computed from inheritance hierarchies and classified according to their characteristics. Further, metrics are evaluated against a case study. These metrics are helpful in comparing alternative inheritance hierarchies at design time to select best alternative, so that the development time and cost can be reduced.