Combining Use Case Diagram and Integrated Definition's IDEFO — A preliminary study

Functional requirements are the statements of services that a system should provide to its users. It is imperative to state explicitly those requirements at the very beginning of system development process, as they act as the basis for the later stages. Normally, this is accomplished through modelling. Modelling enables functional requirements to become apparent to stakeholders. The modelling can be in the form of textual, graphical or even the combination of both. This paper discusses two instances of graphical modelling notations, namely Use Case Diagram (UCD) of Unified Modelling Language (UML) and IDEFO of Integrated Definition Methods (TDEF). It compares the utility of both notations in illustrating the functional requirements of a telecommunication system. The preliminary outcome of the study seems to suggest that UCD and IDEFO respectively have specific limitations, which can be compensated by the strengths of the other. It is therefore envisaged that the usefulness of a model can be improved by having both notations together. The paper concludes the discussion by suggesting a way on how both notations can be used collectively for modelling functional requirements of a system.