Use of Graphical Probabilistic Models to build SIL claims based on software safety standards such as IEC61508-3

MP Brito, JHR May

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

Abstract

Software reliability assessment is ‘different’ from traditional reliability techniques and requires a different process. The use of development standards is common in current good practice. Software safety standards recommend processes to design and assure the integrity of safety-related software. However the reasoning on the validity of these processes is complex and opaque. In this paper an attempt is made to use Graphical Probability Models (GPMs) to formalise the reasoning that underpins the construction of a Safety Integrity Level (SIL) claim based upon a safety standard such as IEC61508 Part 3. There are three major benefits: the reasoning becomes compact and easy to comprehend, facilitating its scrutiny, and making it easier for experts to develop a consensus using a common formal framework; the task of the regulator is supported because to some degree the subjective reasoning which underpins the expert consensus on compliance is captured in the structure of the GPM; the users will benefit from software tools that support implementation of IEC61508, such tools even have the potential to allow cost-benefit analysis of alternative safety assurance techniques.

This report and the work it describes were funded by the Health and Safety Executive. The opinions or conclusions expressed are those of the authors alone and do not necessarily represent the views of the Health and Safety Executive.
Translated title of the contributionUse of Graphical Probabilistic Models to build SIL claims based on safety standards such as IEC615081
Original languageEnglish
Title of host publicationDevelopments in Risk-based Approaches to Safety
Subtitle of host publicationProceedings of the 14th Safety Critical Systems Symposium, 7-9th Feb Bristol UK
EditorsRedmill , Anderson
PublisherSpringer London
Pages241-259
Number of pages19
ISBN (Print)9781846283338
DOIs
Publication statusPublished - 2006

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