Software reuse--the application of existing software artifacts in the development of a new system--has been claimed to dramatically improve system development productivity and quality. These claims have been particularly pronounced with respect to the reuse of object-oriented (OO) software artifacts. However, the empirical evaluations of these claims are relatively sparse and often inconsistent. This paper begins to address the gap in the literature. A verbal-protocol study was conducted in which analysts created a model for a problem (the target) and were given an example problem and solution (the source) to reuse. The results show little support for reuse in OO analysis. First, reuse had no effect on the quality of the OO analysis models. Subjects given a highly reusable example produced solutions that were no better than those of subjects in the control group. Second, the degree of similarity between the source and target problems did have an effect on the reuse process, although it did not impact the reuse outcome. Subjects given the example with the most similarity to the target problem quickly recognized the reuse potential, attempted a fair amount of reuse, but made several errors stemming from lazy copying. Subjects given an example with a lesser (but still significant) degree of similarity were often unable to recognize the reuse potential, and thus engaged in less rescue activity. Thus, the characteristics of the source-target comparison that facilitate noticing the reuse potential of the source do not necessarily help in applying the source solution to the target problem. These results suggest that the claims associated with reuse should be treated with a healthy dose of skepticism.
Object-oriented (OO) analysis, design, and programming techniques have emerged as potential solutions to the software crisis. However, learning OO techniques can be a difficult process. This study investigates students' perceptions of the difficulties in learning and using OO techniques. Two groups of students who had recently completed a sixteen-week course on OO systems development participated in the study. Cognitive mapping techniques implemented with group support system (GSS) technology were used to gather information on the students' perceptions. The groups used the GSS to identify what was difficult about learning and using OO techniques, classify these concepts into categories, rank the relative importance of each category, and determine the relationships among the categories. Importance rankings of the categories show that learning basic object concepts was most important to and most difficult for the students, followed by design issues, and programming techniques. Composite cognitive maps of the shared perceptions of group members suggest that educators and industry trainers can reduce the difficulties of learning OO concepts by teaching simplified methodologies and controlling difficulties of the programming environment.