Refactoring use case models on episodes

Use case models are widely used to capture functional requirements of a system. However, to obtain well-organized use case models is not easy. Refactoring is an approach to reorganize the internal structure of models in order to improve them or extend them in some way. This work looks at refactoring of use case models based on the information captured in episode models. We introduce 10 refactoring rules for use case refactoring in detail, including their verification of the behavior-preserving property. We also present a case study based on the automated teller machine.