Information system requirements: a flow-based diagram versus supplementation of use case narratives with activity diagrams

In developing information system requirements, the exclusive usage of use-case narratives to describe a system's behaviour can cause difficulties for developers who want to ensure a complete description of the embedded process logic. This problem is an instance of the general problem of multiplicity of diagrammatic models in UML instead of a single, integrated diagrammatic model that incorporates function, structure, and behaviour. One approach suggests supplementing use-case narratives with activity diagrams. This paper is a contribution to understanding this ongoing desire to supplement diagrammatic methods with each other, apparently to compensate for the lack of thoroughness of requirements representation in higher-level views of a system. The paper proposes a general solution to the problem by developing a conceptual representation of requirements based on a new flow-based diagrammatic model. To demonstrate this approach in a specific context, the paper focuses on a single attempt to supplement a use-case narrative with activity diagrams by recasting it in terms of the flow-based solution. The results indicate that the use-case narrative not only is incomplete in details, but also may have chronological gaps.