Design Patterns in Software Maintenance: An Experiment Replication at University of Alabama

Design patterns are widely used within the software engineer community. Researchers claim that design patterns improve software quality. In this paper, we describe two experiments, using graduate student participants, to study whether design patterns improve the software quality, specifically maintainability and understandability. We replicated a controlled experiment to compare the maintainability of two implementations of an application, one using a design pattern and the other using a simpler alternative. The maintenance tasks in this replication experiment required the participants to answer questions about a Java program and then modify that program. Prior to the replication, we performed a preliminary exercise to investigate whether design patterns improve the understandability of software designs. We gave the participants the graphical design of the systems that would be used in the replication study. The participant received either the version of the design containing the design pattern or the version containing the simpler alternative. We asked the participants a series of questions to see how well they understood the given design. The results of two experiments revealed that the design patterns did not improve either the maintainability or the understandability of the software. We found that there was no significant correlation between the maintainability and the understandability of the software even though the participants had received the design of the systems before they performed the maintenance tasks.