Making Software Product Line Evolution Safer

Developers evolve software product lines (SPLs) manually or using typical program refactoring tools. However, when evolving a product line to introduce new features or to improve its design, it is important to make sure that the behavior of existing products is not affected. Typical program refactorings cannot guarantee that because the SPL context goes beyond code and other kinds of core assets, and involves additional artifacts such as feature models and configuration knowledge. Besides that, in a SPL we typically have to deal with a set of possibly alternative assets that do not constitute a well-formed program. As a result, manual changes and existing program refactoring tools may introduce behavioral changes or invalidate existing product configurations. To avoid that, we propose approaches and implement tools for making product line evolution safer; these tools check whether SPL transformations are refinements in the sense that they preserve the behavior of the original SPL products. They implement different and practical approximations of a formal definition of SPL refinement. We evaluate the approaches in concrete SPL evolution scenarios where existing product's behavior must be preserved. However, our tools found that some transformations introduced behavioral changes. Moreover, we evaluate defective refinements, and the toolset detects the behavioral changes.