Variability evolution and erosion in industrial product lines - a case study

Successful software products evolve continuously to meet the changing stakeholder requirements. For software product lines, modifying variability is an additional challenge that must be carefully tackled during the evolution of the product line. This bears considerable challenges for industry as understanding on how variability implementations advance over time is not trivial. Moreover, it may lead to an erosion of variability, which needs an investigation of techniques on how to identify the variability erosion in practice, especially in the source code. To address this problem, we have investigated the evolution of a large-scale industrial product line over a period of 4 years. Along improvement goals, we have researched a set of appropriate metrics and measurement approaches, applied them in this case study and interpreted the results. Main contributions of the paper comprise (i) industrial experience with product line evolution, taken improvement steps and their actual effects, (ii) an in depth discussion of the conducted case study including method, goals, and metrics, and (iii) the measured results and identified erosion symptoms