Use cases describe a set of interactions between actors/users and the system under study. These interactions should be described textually according to some style and template to be simultaneously readable, consistent and verifiable. The main reason for these qualities is that use cases specification should be used both by business analysts and requirements engineers, when specifying functional requirements, as well as by software developers, when designing and implementing the involved system functionality. In spite of the popularity of use cases, there are not many patterns and guidance to help produce use cases specifications in a systematic and high-quality way. Furthermore, in the context of Model Driven Development (MDD) approaches, use cases specifications can be also considered models with precise syntax and semantics to be automatically validated or used in model-to-model or model-to-text transformations.

In this paper we propose a pattern language to improve the quality of use cases specifications. These patterns are concrete guidelines that have emerged from the research and industrial experience of the authors throughout the years, particularly in the designing of MDD languages and approaches and in applying them in concrete applications. These patterns are interconnected among themselves and are the following: (P1) Define Use Case Types, (P2) Keep Use Case Consistent with the Domain Model, (P3) Define Use Case with Different Scenario and Interaction Block Types, and (P4) Define Use Case with Different Action Types.