The Evolution of Design Pattern Grime: An Industrial Case Study

Context: GoF design patterns are popular among both researchers and practitioners, in the sense that software can be largely comprised of pattern instances. However, there are concerns regarding the efficacy with which software engineers maintain pattern instances, which tend to decay over the software lifetime if no special emphasis is placed on them. Pattern grime (i.e., degradation of the instance due to buildup of unrelated artifacts) has been pointed out as one recurrent reason for the decay of GoF pattern instances. Goal: Seeking to explore this issue, we investigate the existence of relations between the accumulation of grime in pattern instances and various related factors: (a) projects, (b) pattern types, (c) developers, and (d) the structural characteristics of the pattern participating classes. Method: For that, we empirically assessed these relations through an industrial exploratory case study involving five projects (approx. 260,000 lines of code). Results: Our findings suggest a linear accumulation of pattern grime, which may depend on pattern type and developer. Moreover, we present and discuss a series of correlations between the accumulation of pattern grime and structural characteristics. Conclusions: The outcome of our study can benefit both researchers and practitioners, as it points to interesting future work opportunities and also implications relevant to the refinement of best practices, the raise awareness among developers, and the monitoring of pattern grime accumulation.