Evaluation of a Specification Approach for Vehicle Functions using Activity Diagrams in Requirements Documents

Abstract

Rising complexity of systems has long been a major challenge in requirements engineering. This manifests in more extensive and harder to understand requirements documents. At the Daimler AG, an approach is applied that combines the use of activity diagrams with natural language specifications to specify vehicle functions. The approach starts with an activity diagram that is created to get an early overview. The contained information is then transferred to a textual requirements document, where details are added and the behavior is refined. While the approach aims at reducing efforts needed to understand a function’s behavior, the application of the approach itself causes new challenges on its own. By examining existing specifications at Daimler, we identified nine categories of inconsistencies and deviations between activity diagrams and their textual representations. This paper extends a previous case study on the subject by presenting additional data we acquired. Our analysis indicates that a coexistence of textual and graphical representations of models without proper tool support results in inconsistencies and deviations that may cause severe maintenance costs or even provoke faults in subsequent development steps.