Are Forward Designed or Reverse-Engineered UML Diagrams More Helpful for Code Maintenance?: A Controlled Experiment

Abstract

Context: UML has been the de facto standard notation for modeling object-oriented software systems since its appearance in 1997. UML diagrams are important for maintainers of a system, especially when the software was developed by a different team. These diagrams of the system are not always available, however, and are commonly recovered using Reverse Engineering (RE) techniques. When obtained through RE, UML diagrams have a high level of detail as compared to those developed in the forward design activity. Method: In this paper we report on a comparison of the attitude and performance of maintainers when using these two kinds of diagrams during the maintenance of source code. Our findings were obtained by carrying out a controlled experiment with 40 students of a Master’s degree in Computer Science. Results: The results show a preference for forward design diagrams but do not display significant differences in task performance. The post-experiment survey results have led us to conclude that the subjects did not consider RE diagrams helpful; they found them difficult to understand, particularly the sequence diagrams. In the case of forward design diagrams, subjects considered sequence diagrams as useful, but they did not really employ them. Conclusions: Based on our findings, as regards performance of maintainers, there are no objective results which favor the use of one of these types of diagram in particular, i.e., UML diagrams which come from forwards design, on the one hand, and diagrams obtained from RE, on the other. Subjective opinions do, however, lead us to recommend the use of diagrams created during design. Nevertheless, we realize that the results should be considered as preliminary ones; further replications of this experiment are planned, using students and professionals, the aim being to obtain more conclusive results.