Author(s)

A. Cointet & C. Laval

Abstract

This paper sets out to analyze, within the framework of a development or of an upgrade of a system, how the logic of requirements definition impacts on the relevance of identification and evaluation of the risks. This is true all the more as the system is complex and questions raised by the relation between requirement and level of safety and security are numerous:  How can we guarantee that needs and constraints identified in the \“customer” specifications constitute the complete set of requirements attached to the various functions, and that they are optimized for the targeted uses?  How can we help the \“customer” to express the multiple aspects of needs by keeping distance with technical solutions?  How can we distinguish the safety and security functions?  How can we bring to light that the same function can have different safety and security levels, according to the contexts of system use?  How can we deal with safety functions of segregated levels?  How can we identify the risks connected to the non-compliance with these requirements or to the inadequacy of requirements? The paper suggests showing, on the basis of an example, how a rigorous systemic and functional approach and concepts of defence in-depth allow wider points of view, structure the requirements and facilitate the identification of the risks. Keywords: functional analysis, system engineering, defence in depth. The Sustainable World 537 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and the Environment, Vol 142, © 2010 WIT Press doi:

Keywords

functional analysis, system engineering, defence in depth