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978-3-86853-963-9, Reihe Informatik

Christoph Knieke
Modellierung und Validierung von ausführbaren Anforderungsspezifikationen mit erweiterten UML Aktivitätsdiagrammen

214 Seiten, Dissertation Technische Universität Braunschweig (2011), Softcover, A5

Zusammenfassung / Abstract

Nowadays, the requirements elicitation and specification phase, in which the requirements for a system are obtained from users, is essential for developing software systems. Errors occurring during the phase of requirements elicitation and specification have turned out to be major reasons for the failure of IT projects. Particularly, errors occur as requirements are specified erroneous and as requirements have inconsistencies and incompletenesses.

Errors during the phase of requirements elicitation and specification can be avoided by choosing an appropriate specification language enabling the validation of the requirements by users. In this work, we consider activity diagrams for the specification of system requirements as activity diagrams possess a high level of abstraction and a workflow-oriented view, and thus are well suited for the early development phase. Activity diagrams are behavior diagrams of the Unified Modeling Language (UML), and offer graphical representations of control and data flows between elementary actions.

In this thesis, an operational semantics for UML 2 activity diagrams is defined as a basis for tool development. The operational semantics paves the way for validation by simulation of a requirements specification based on activity diagrams. As the informal semantics of the UML contains many unclarities, several detailed definitions of the semantics are given.

However, certain kinds of requirements like mandatory and forbidden behavior can not be expressed by UML activity diagrams. Thus, similar to the language of Live Sequence Charts, an extension for UML 2 activity diagrams is proposed, socalled Live Activity Diagrams (LADs). By checking, whether violations of mandatory behavior or forbidden behavior occur, errors like inconsistencies and incompletenesses in the requirements can be uncovered.

Based on the executable step semantics of LADs, a tool platform has been implemented enabling the modeling, simulation, and validation of LAD models. During validation, the model is stimulated by sequences of user inputs, and reactions of the system according to the user inputs are observed.

By a connection between the tool and the Lego Mindstorms NXT platform, NXT robots are controlled by behavior that is specified by LADs. Specification errors are revealed by monitoring the moving NXT robots. The approach proposed in this thesis is confirmed by several case studies as well as the prototypical tool development.