A controlled experiment in maintenance: comparing design patterns to simpler solutions

Abstract

ÐSoftware design patterns package proven solutions to recurring design problems in a form that simplifies reuse. We are seeking empirical evidence whether using design patterns is beneficial. In particular, one may prefer using a design pattern even if the actual design problem is simpler than that solved by the pattern, i.e., if not all of the functionality offered by the pattern is actually required. Our experiment investigates software maintenance scenarios that employ various design patterns and compares designs with patterns to simpler alternatives. The subjects were professional software engineers. In most of our nine maintenance tasks, we found positive effects from using a design pattern: Either its inherent additional flexibility was achieved without requiring more maintenance time or maintenance time was reduced compared to the simpler alternative. In a few cases, we found negative effects: The alternative solution was less error-prone or required less maintenance time. Although most of these effects were expected, a few were surprising: A negative effect occurs although a certain application of the Observer pattern appears to be well justified and a positive effect occurs despite superfluous flexibility (and, hence, complexity) introduced by a certain application of the Decorator pattern. Overall, we conclude that, unless there is a clear reason to prefer the simpler solution, it is probably wise to choose the flexibility provided by the design pattern because unexpected new requirements often appear. We identify several questions for future empirical research.

Relationship between design patterns defects and crosscutting concern scattering degree: an empirical study

“…He found that some patterns, such as Observer and Singleton, are correlated with large code structures and are likely to be more fault prone. Prechelt et al [27] performed a series of controlled experiments with the aim of comparing design patterns with alternative, simpler solutions to perform maintenance tasks. They found that the code developed using design patterns contained a lower number of defects than the code developed using alternative design strategies.…”

An empirical study of the relationships between design pattern roles and class change proneness

“…Prechelt et al [18] performed a series of controlled experiments to compare design motifs with alternative, simpler solutions to assess their impact on maintenance tasks.…”

Relating the Evolution of Design Patterns and Crosscutting Concerns

“…As a future work, we aim to extract the evolution of such aspect oriented re-factoring changes to show if the code quality improves in time by looking, for example, at defect density. Regarding the analysis of design pattern evolution, Bieman et al [2] analyzed four small size systems and one large size system to identify the observable effects of the use of design patterns, such as pattern change proneness; Vokáč [27] analyzed the corrective maintenance of a large commercial product over three years, comparing defect rates for classes that participated in design patterns versus those that did not participate; Prechelt et al [24] performed a series of controlled experiments with the aim of comparing design patterns with alternative, simpler solutions to perform maintenance tasks.…”