Bayesian Networks for Dependability Analysis: an Application to Digital Control Reliability

Bayesian Networks (BN) provide robust probabilistic methods of reasoning under un­ certainty, but despite their formal grounds are strictly based on the notion of condi­ tional dependence, not much attention has been paid so far to their use in dependability analysis. The aim of this paper is to pro­ pose BN as a suitable tool for dependability analysis, by challenging the formalism with basic issues arising in dependability tasks. We will discuss how both modeling and anal­ ysis issues can be naturally dealt with by BN. Moreover, we will show how some limi­ tations intrinsic to combinatorial dependabil­ ity methods such as Fault Trees can be over­ come using BN. This will be pursued through the study of a real-world example concerning the reliability analysis of a redundant digital Programmable Logic Controller (PLC) with majority voting 2:3