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Interactive Visualizations Supporting Minimal Cut Set Analysis II

  • The Context and Its Importance: In safety and reliability analysis, the information generated by Minimal Cut Set (MCS) analysis is large. The Top Level event (TLE) that is the root of the fault tree (FT) represents a hazardous state of the system being analyzed. MCS analysis helps in analyzing the fault tree (FT) qualitatively-and quantitatively when accompanied with quantitative measures. The information shows the bottlenecks in the fault tree design leading to identifying weaknesses of the system being examined. Safety analysis (containing the MCS analysis) is especially important for critical systems, where harm can be done to the environment or human causing injuries, or even death during the system usage. Minimal Cut Set (MCS) analysis is performed using computers and generating a lot of information. This phase is called MCS analysis I in this thesis. The information is then analyzed by the analysts to determine possible issues and to improve the design of the system regarding its safety as early as possible. This phase is called MCS analysis II in this thesis. The goal of my thesis was developing interactive visualizations to support MCS analysis II of one fault tree (FT). The Methodology: As safety visualization-in this thesis, Minimal Cut Set analysis II visualization-is an emerging field and no complete checklist regarding Minimal Cut Set analysis II requirements and gaps were available from the perspective of visualization and interaction capabilities, I have conducted multiple studies using different methods with different data sources (i.e., triangulation of methods and data) for determining these requirements and gaps before developing and evaluating visualizations and interactions supporting Minimal Cut Set analysis II. Thus, the following approach was taken in my thesis: 1- First, a triangulation of mixed methods and data sources was conducted. 2- Then, four novel interactive visualizations and one novel interaction widget were developed. 3- Finally, these interactive visualizations were evaluated both objectively and subjectively (compared to multiple safety tools) from the point of view of users and developers of the safety tools that perform MCS analysis I with respect to their degree in supporting MCS analysis II and from the point of non-domain people using empirical strategies. The Spiral tool supports analysts with different visions, i.e., full vision, color deficiency protanopia, deuteranopia, and tritanopia. It supports 100 out of 103 (97%) requirements obtained from the triangulation and it fills 37 out of 39 (95%) gaps. Its usability was rated high (better than their best currently used tools) by the users of the safety and reliability tools (RiskSpectrum, ESSaRel, FaultTree+, and a self-developed tool) and at least similar to the best currently used tools from the point of view of the CAFTA tool developers. Its quality was higher regarding its degree of supporting MCS analysis II compared to the FaultTree+ tool. The time spent for discovering the critical MCSs from a problem size of 540 MCSs (with a worst case of all equal order) was less than a minute while achieving 99.5% accuracy. The scalability of the Spiral visualization was above 4000 MCSs for a comparison task. The Dynamic Slider reduces the interaction movements up to 85.71% of the previous sliders and solves the overlapping thumb issues by the sliders provides the 3D model view of the system being analyzed provides the ability to change the coloring of MCSs according to the color vision of the user provides selecting a BE (i.e., multi-selection of MCSs), thus, can observe the BEs' NoO and provides its quality provides two interaction speeds for panning and zooming in the MCS, BE, and model views provide a MCS, a BE, and a physical tab for supporting the analysis starting by the MCSs, the BEs, or the physical parts. It combines MCS analysis results and the model of an embedded system enabling the analysts to directly relate safety information with the corresponding parts of the system being analyzed and provides an interactive mapping between the textual information of the BEs and MCSs and the parts related to the BEs. Verifications and Assessments: I have evaluated all visualizations and the interaction widget both objectively and subjectively, and finally evaluated the final Spiral visualization tool also both objectively and subjectively regarding its perceived quality and regarding its degree of supporting MCS analysis II.

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Author:Yasmin Al-Zokari
URN (permanent link):urn:nbn:de:hbz:386-kluedo-44123
Advisor:Hans Hagen, Peter Dannenmann, Curtis Smith
Document Type:Doctoral Thesis
Language of publication:English
Publication Date:2016/07/07
Year of Publication:2016
Publishing Institute:Technische Universität Kaiserslautern
Granting Institute:Technische Universität Kaiserslautern
Acceptance Date of the Thesis:2016/06/03
Date of the Publication (Server):2016/07/07
Tag:Minimal Cut Set Visualization
Number of page:XVIII, 675
Faculties / Organisational entities:Fachbereich Informatik
DDC-Cassification:0 Allgemeines, Informatik, Informationswissenschaft / 004 Informatik
Licence (German):Standard gemäß KLUEDO-Leitlinien vom 30.07.2015