Scheduling of conflicting refactorings to promote quality improvement

Software refactoring is to restructure object-oriented software to improve its quality, especially extensibility, reusability and maintainability while preserving its external behaviors. For a special software system, there are usually quite a few refactorings available at the same time. But these refactorings may conflict with each other. In other words, carrying out a refactoring may disable other refactorings. Consequently, only a subset of the available refactorings can be applied together, and which refactorings will be applied depends on the schedule (application order) of the refactorings. Furthermore, carrying out different subsets of the refactorings usually leads to different improvement of software quality. As a result, in order to promote the improvement of software quality, refactorings should be scheduled rationally. However, how to schedule refactorings is rarely discussed. Usually, software engineers carry out refactorings immediately when they are found out. They do not wait until all applicable refactorings are found out and scheduled. In other words, the refactorings are not scheduled explicitly, and conflicts among them are not taken into consideration. Though more and more refactorings are formalized and automated by refactoring tools, refactoring tools apply refactorings usually in a nondeterministic fashion (in random). In this paper, we propose a scheduling approach to schedule conflicting refactorings to promote the improvement of software quality achieved by refactorings. Conflicts among refactorings are detected, and then a scheduling model is presented. And then a heuristic algorithm is proposed to solve the scheduling model. Results of experiments suggest that the proposed scheduling approach is effective in promoting the improvement of software quality.