Refactoring of Statecharts

Abstract

Statecharts are an important tool for specifying the behavior of reactive systems, and development tools can automatically generate object-oriented code from them. As the system is refactored, it is necessary to modify the associated statecharts as well, performing operations such as grouping or ungrouping states, extracting part of a statechart into a separate class, and merging states and transitions. Refactoring tools embedded in object-oriented development environments are making it much easier for developers to modify their programs. However, tool support for refactoring statecharts does not yet exist. As a result, developers avoid making certain changes that are too difficult to perform manually, even though design quality deteriorates.Methodologically, statecharts were meant to enable a systems engineer to describe a complete system, which would then be refined into a concrete implementation (object-oriented or other). This process is not supported by object-oriented development environments, which force each statechart to be specified as part of a class. Automated tool support for refactoring statecharts will also make this kind of refinement possible.This paper describes a case study that shows the usefulness of refactoring support for statecharts, and presents an initial catalog of relevant refactorings. We show that a top-down refinement process helps identify the tasks and classes in a natural way.KeywordsParallel ComponentSeparate ClassSeparate TaskBottom ComponentHead ProcessingThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.