A Framework for Dependability analysis of software systems with trusted bases

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 73-76).A new approach is suggested for arguing that a software system is dependable. The key idea is to structure the system so that highly critical requirements are localized in small subsets of the system called trusted bases. In most systems, the satisfaction of a requirement relies on assumptions about the environment, in addition to the behavior of software. Therefore, establishing a trusted base for a critical property must be carried out as early as the requirements phase. This thesis proposes a new framework to support this activity. A notation is used to construct a dependability argument that explains how the system satisfies critical requirements. The framework provides a set of analysis techniques for checking the soundness of an argument, identifying the members of a trusted base, and illustrating the impact of failures of trusted components. The analysis offers suggestions for redesigning the system so that it becomes more reliable. The thesis demonstrates the effectiveness of this approach with a case study on electronic voting systems.by Eunsuk Kang.S.M

Building dependability arguments for software intensive systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 301-308).A method is introduced for structuring and guiding the development of end-to-end dependability arguments. The goal is to establish high-level requirements of complex software-intensive systems, especially properties that cross-cut normal functional decomposition. The resulting argument documents and validates the justification of system-level claims by tracing them down to component-level substantiation, such as automatic code analysis or cryptographic proofs. The method is evaluated on case studies drawn from the Burr Proton Therapy Center, operating at Massachusetts General Hospital, and on the Pret a Voter cryptographic voting system, developed at the University of Newcastle.by Robert Morrison Seater.Ph.D

Coherence check of behavioural specifications against specific properties of the operational context

In der Anforderungsspezifikation eines Systems werden Eigenschaften definiert, die das System an seiner Schnittstelle zur Umgebung aufweisen muss, um im Betrieb seinen Zweck zu erfüllen. Eine Vielzahl von Untersuchungen zeigt, dass Fehler in der Anforderungsspezifikation zu erheblichen negativen Konsequenzen sowohl im Entwicklungsprozess des Systems als auch im Systembetrieb führen können. Fehler in der Anforderungsspezifikation sind dabei oftmals auf Kohärenzbrüche gegenüber dem operationellen Kontext zurückzuführen, d. h. auf ungültige oder unvollständige Annahmen über die Umgebung, in der das System betrieben werden soll. Im Rahmen des Dissertationsvorhabens wurde ein teilautomatisierter Ansatz entwickelt, der darauf abzielt, Kohärenzbrüche in der Anforderungsspezifikation von Systemen gegenüber dem operationellen Kontexts dieser Systeme aufzudecken. Die Arbeit fokussiert dabei auf die Verhaltensspezifikation als Teil der Anforderungsspezifikation sowie auf Eigenschaften des operationellen Kontexts in der statisch-strukturellen Perspektive. Der entwickelte Ansatz setzt sich aus einem Rahmenwerk zur Modellierung des operationellen Kontexts in der statisch-strukturellen Perspektive und einem Katalog von Formalismen zusammen, durch deren Anwendung Kohärenzbrüche in der Verhaltensspezifikation teilautomatisiert aufgedeckt werden können. Zur Evaluation des Ansatzes wurde dieser exemplarisch auf die Verhaltensspezifikation eines von Komplexität und Umfang her praxistypischen Systems angewendet. Zum Nachweis der technischen Umsetzbarkeit des Ansatzes wird ein Werkzeugprototyp vorgestellt. Der entwickelte Ansatz liefert einen Beitrag im Hinblick auf Techniken zur differenzierten Modellierung des operationellen Kontexts von Systemen in der statisch-strukturellen Perspektive und zur teilautomatisierten analytischen Qualitätssicherung von Anforderungsspezifikationen.The requirements specification of a system contains the definition of properties the system must exhibit at its interfaces with the environment in order to meet its purpose during system operation. There is ample evidence in the literature that suggests that errors in the requirements specification may lead to serious negative consequences during the development process of the system as well as subsequently, during system operation. Errors in the requirements specification can often be traced back to the fact that the specification is not coherent with the operational context due to invalid or incomplete assumptions about the system’s operating environment. In the context of this dissertation, a semi-automated approach was developed, aiming at detecting coherence defects within a system’s requirements specification against its operational context. The focus of this thesis lies on the specification of the system’s behaviour as part of the requirements specification and on properties of the operational context in the structural perspective. An approach has been developed that consists of a framework for modelling the operational context in the structural perspective. Furthermore, a list of formalisms has been devised, which allow detecting coherence defects in the specification of the system’s behaviour in a partially automated way. For validation purposes, the approach was exemplarily applied to the specification of a system that renders a typical real-world example with regard to complexity and extent. To prove the technical feasibility of the approach, a tool prototype is presented. The dissertation provides a contribution with regard to techniques for modelling the operational context of systems in the structural perspective as well as for the partially automated, analytic quality assurance of requirements specification