Reasoning About Confidence and Uncertainty in Assurance Cases: A Survey

Abstract

Assurance cases are structured logical arguments supported by evidence that explain how systems, possibly software systems, satisfy desirable properties for safety, security or reliability. The confidence in both the logical reasoning and the underlying evidence is a factor that must be considered carefully when evaluating an assurance case; the developers must have confidence in their case before the system is delivered and the assurance case reviewer, such as a regulatory body, must have adequate confidence in the case before approving the system for use. A necessary aspect of gaining confidence in the assurance case is dealing with uncertainty, which may have several sources. Uncertainty, often impossible to eliminate, nevertheless undermines confidence and must therefore be sufficiently bounded. It can be broadly classified into two types, aleatory (statistical) and epistemic (systematic). This paper surveys how researchers have reasoned about uncertainty in assurance cases. We analyze existing literature to identify the type of uncertainty addressed and distinguish between qualitative and quantitative approaches for dealing with uncertainty.

Uncertainty Elicitation and Propagation in GSN Models of Assurance Cases

“…It guarantees that all clear-cut decisions (rejection or acceptance) are made only when the confidence level is maximal. To avoid negative belief and disbelief values, we must adjust the decision value to respect constraint (5). Therefore, when Dec(p) < 1−Conf (p) 2 (rejection: black dots in Fig.…”

Assurance Case for Safety and Security Implementation: A Survey of Applications

“…Normative models of informal argumentation do not offer clear guidance on when an argument should cite evidence rather than appeal to a more detailed argument. So, improvement of argumentation stimulated a lot of papers devoted to this issue [34,35], taking into account that there is not any completed agreement which kind of evidence could be completely sufficient.…”

“…The paper [34] surveys how researchers have reasoned uncertainty in assurance cases. The types of uncertainties are addressed and distinguished between qualitative and quantitative approaches.…”

Confidence assessment in safety argument structure - Quantitative vs. qualitative approaches

“…Several works already proposed mathematical models to quantify and propagate confidence/uncertainty in graphical representations of argument structures like GSN. Graydon and Holloway [1], as well as Duan et al [2], stated and discussed proposals that deal with the issue of uncertainty. An important number of approaches used probability theory to model uncertainty and propagate it with Bayesian networks [3,4].…”