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Exploring the impact of different cost heuristics in the allocation of safety integrity levels

Azevedo, Luís Silva; Parker, David; Papadopoulos, Yiannis; Walker, Martin; Sorokos, Ioannis; Arau?jo, Rui Esteves


Luís Silva Azevedo

Martin Walker

Ioannis Sorokos

Rui Esteves Arau?jo


Contemporary safety standards prescribe processes in which system safety requirements, captured early and expressed in the form of Safety Integrity Levels (SILs), are iteratively allocated to architectural elements. Different SILs reflect different requirements stringencies and consequently different development costs. Therefore, the allocation of safety requirements is not a simple problem of applying an allocation "algebra" as treated by most standards; it is a complex optimisation problem, one of finding a strategy that minimises cost whilst meeting safety requirements. One difficulty is the lack of a commonly agreed heuristic for how costs increase between SILs. In this paper, we define this important problem; then we take the example of an automotive system and using an automated approach show that different cost heuristics lead to different optimal SIL allocations. Without automation it would have been impossible to explore the vast space of allocations and to discuss the subtleties involved in this problem.


Azevedo, L. S., Parker, D., Papadopoulos, Y., Walker, M., Sorokos, I., & Araújo, R. E. (2014). Exploring the impact of different cost heuristics in the allocation of safety integrity levels. Lecture notes in computer science, 8822, 70-81.

Acceptance Date Jan 1, 2014
Publication Date Jan 1, 2014
Deposit Date Feb 29, 2016
Publicly Available Date Feb 29, 2016
Journal Lecture notes in computer science
Print ISSN 0302-9743
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 8822
Pages 70-81
Series Title Lecture Notes in Computer Science
Book Title Model-Based Safety and Assessment; Lecture Notes in Computer Science
ISBN 9783319122137; 9783319122144
Keywords Dependability analysis, Requirements analysis, Functional safety, SIL allocation and decomposition, Cost optimisation
Public URL
Publisher URL
Additional Information This is an author's accepted manuscript of a paper published in Lecture notes on computer science, 2014, v.8822. The final publication is available at Springer via
Contract Date Feb 29, 2016


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