Refining use cases through temporal relations

In UML, use cases can be used both for modeling the external requirements of a subject (system) and the functionality offered by a subject. Moreover, use cases can also be used to specify the requirements the subject poses on its environment, by defining how the actors should interact with the subject. Task models are used in the HCI community to model tasks the user and the system must carry out when interacting. In contrast with task-models, temporal relations are not allowed within use case models. This paper proposes three temporal relations between use cases, making possible the inclusion of more detail in the use case model, thus enhancing the expressiveness of use cases for modeling requirements and contributing to better user interface (UI) models generation, within the context of an automatic model-to-model transformation process between a use case model and a UI model.