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In systems engineering, dependability is a measure of a system's availability, reliability, and its maintainability.〔() (search for dependability)〕 This may also encompass mechanisms designed to increase and maintain the dependability of a system.〔A. Avizienis, J.-C. Laprie, B. Randell, and C. Landwehr, "(Basic Concepts and Taxonomy of Dependable and Secure Computing )," IEEE Transactions on Dependable and Secure Computing, vol. 1, pp. 11-33, 2004.〕 The International Electrotechnical Commission (IEC), via its Technical Committee TC 56 develops and maintains international standards that provide systematic methods and tools for dependability assessment and management of equipment, services, and systems throughout their life cycles. Dependability can be broken down into three elements: * Attributes - A way to assess the dependability of a system * Threats - An understanding of the things that can affect the dependability of a system * Means - Ways to increase a system's dependability == History == Some sources hold that word was coined in the nineteen-teens in Dodge Brothers automobile print advertising. But the word predates that period, with the Oxford English Dictionary finding its first use in 1901. As interest in fault tolerance and system reliability increased in the 1960s and 1970s, dependability came to be a measure of () as measures of reliability came to encompass additional measures like safety and integrity.〔Brian Randell, "Software Dependability: A Personal View", in the Proc of the 25th International Symposium on Fault-Tolerant Computing (FTCS-25), California, USA, pp 35-41, June 1995.〕 In the early 1980s, Jean-Claude Laprie thus chose ''dependability'' as the term to encompass studies of fault tolerance and system reliability without the extension of meaning inherent in ''reliability''.〔J.C. Laprie. "Dependable Computing and Fault Tolerance: Concepts and terminology," in Proc. 15th IEEE Int. Symp. on Fault-Tolerant Computing, 1985〕 The field of dependability has evolved from these beginnings to be an internationally active field of research fostered by a number of prominent international conferences, notably the International Conference on Dependable Systems and Networks, the International Symposium on Reliable Distributed Systems and the International Symposium on Software Reliability Engineering. Dependability for a system incorporates the following attributes or unfunctional requirements: * Availability: readiness for correct service * Reliability: continuity of correct service * Maintainability: to undergo modifications and repairs and combines them with the concepts of threats and failures to create dependability. Since the 1980s, safety and security have been added to measures of dependability.〔A. Avizienis, J.-C. Laprie and B. Randell: ''(Fundamental Concepts of Dependability )''. Research Report No 1145, LAAS-CNRS, April 2001〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「dependability」の詳細全文を読む スポンサード リンク
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