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Research paper : A methodology for improving reliability of complex systems (A. Katoh et al.)−198−Synthesiology - English edition Vol.3 No.3 (2010) systems engineering were started mainly in the military and aerospace fields, and systems engineering evolved through the accumulating and reflecting of “best practices” of the system development. The systems engineering process is standardized as know-hows and rules independent of technological fields[8]-[10]. Architectural design method is defined as a part of the systems engineering process. Architectural designing is a method to allocate the functions and performances required of a system to the system components, and to define the specifications of the components and the interface among the components. By architectural designing according to the standardized process, the complex system can be decomposed into its components smoothly and surely. In this paper, standardized architectural design method is simply called “architectural design method”.Model checking is a method to verify whether a given property is valid or invalid in all possible state transitions which can be achieved by the models which represent the state transitions of the system, using a computer exhaustively. Model checking is one of the formal methods[11] Term 10. Model checking is already established as a verification method, and nowadays is popular in software development. According to the functional safety standard IEC 61508[12] Term 11, applying the formal method is recommended for the system development, and it is gaining attention as a method for achieving the high reliability of the system. Whether the properties which must be satisfied by the cooperative behavior is valid or not is thoroughly verified by applying model checking to the specifications for the cooperative behavior between components. As a result, it is possible to detect inconsistency of the cooperative behavior which may occur in the complex states.Architectural design method is systematic knowledge which is formed by collecting best practices in the system design fields based on systems engineering. Model checking is a research result which improves the reliability in the system verification field, based on mathematical logic and computer science. In this research, we aim to achieve the high reliability in the complex systems, synthesizing architectural design method and model checking, and develop a methodology which utilizes the characteristic of both methods. Our research corresponds to Type 2 Basic Research which widely selects the knowledge of different technological fields and synthesizes them to satisfy social and economic needs.This paper describes a methodology for decomposing a system specification into component specifications and interface specifications among components whose cooperative behavior is consistent with each component. It also describes the research process of this methodology. It is structured as follows. Chapter 2 describes the research goal and the research scenario. Chapter 3 describes architectural design method and model checking. Chapter 4 describes the synthesis process of architectural design method and model checking. Chapter 5 describes the application of an industrial use. Chapter 6 discusses the effectiveness and issues of this methodology. Chapter 7 summarizes this paper and describes the future work.2 Research objective and research scenarioThe objective of this research is to establish a methodology for decomposing a system specification into component specifications and interface specifications among components whose cooperating behavior is consistent with each component, which is not specific to particular technological systems. Figure 1 shows the research scenario. For the research scenario to achieve the research objective, the methods whose effectiveness has been fully verified are selected among the technological fields related to the system development. The reason for this is that a high-quality methodology can be established efficiently by employing methods which are already recognized as being effective for the system development. The methodology is established by synthesizing the selected methods to maximize their characteristics. The reason for this is that there is a possibility to produce a new research or technological field through developing a new technology by the synthesis of methods from different researches or technological fields. Also, the effectiveness of methodology is evaluated by applying this methodology to an actual case in industry. There are two reasons for selecting the industrial case as the application. The first reason is that in order to evaluate the practical applicability of this methodology in industry, it is necessary to take a functionally complex case as the application to consider safety, rather than a mere sample. The second reason is that by propagating the effectiveness of this methodology to industry, it may be possible to bridge the gap between the research activities and the social contributions of the research results, or the so-called valley of death.3 Selection of methodsIn establishing the methodology in this research, the functions which must be satisfied by the methodology are Fig. 1 Research scenario MethodMethodMethodAchievement of research objectiveApplication ofmethodology toindustrial caseSynthesis oftechnologies utilizingtheir characteristicsSelection of technologiesrecognized to be effectiveTechnological field relatedto system developmentResearch flowIndustrial caseEstablishment of methodology in this research

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