Facilitating the transition from use case models to analysis models: Approach and experiments

Use case modeling, including use case diagrams and use case specifications (UCSs), is commonly applied to structure and document requirements. UCSs are usually structured but unrestricted textual documents complying with a certain use case template. However, because Use Case Models (UCMods) remain essentially textual, ambiguity is inevitably introduced. In this article, we propose a use case modeling approach, called Restricted Use Case Modeling (RUCM), which is composed of a set of well-defined restriction rules and a modified use case template. The goal is two-fold: (1) restrict the way users can document UCSs in order to reduce ambiguity and (2) facilitate the manual derivation of initial analysis models which, when using the Unified Modeling Language (UML), are typically composed of class diagrams, sequence diagrams, and possibly other types of diagrams.

Though the proposed restriction rules and template are based on a clear rationale, two main questions need to be investigated. First, do users find them too restrictive or impractical in certain situations? In other words, can users express the same requirements with RUCM as with unrestricted use cases? Second, do the rules and template have a positive, significant impact on the quality of the constructed analysis models? To investigate these questions, we performed and report on two controlled experiments, which evaluate the restriction rules and use case template in terms of (1) whether they are easy to apply while developing UCMods and facilitate the understanding of UCSs, and (2) whether they help users manually derive higher quality analysis models than what can be generated when they are not used, in terms of correctness, completeness, and redundancy. This article reports on the first controlled experiments that evaluate the applicability of restriction rules on use case modeling and their impact on the quality of analysis models. The measures we have defined to characterize restriction rules and the quality of analysis class and sequence diagrams can be reused to perform similar experiments in the future, either with RUCM or other approaches.

Results show that the restriction rules are overall easy to apply and that RUCM results into significant improvements over traditional approaches (i.e., with standard templates, without restrictions) in terms of class correctness and class diagram completeness, message correctness and sequence diagram completeness, and understandability of UCSs.