Irrational System Behavior in a System of Systems

System of systems (SoS) failures can sometimes be traced to a system within the SoS behaving in unexpected ways. Due to their emergent complexity, these types of failures are notoriously challenging to foresee. This paper presents a method to aid in predicting unknown unknowns in a SoS. Irrationality initiators – failure flows emanating from one system that serve as unexpected initiating events in another system – are introduced into quantitative risk analysis methods such as the Failure Flow Identification and Propagation framework and Probabilistic Risk Assessment. Analysis of models built using this approach yield a probability distribution of failure paths through a system within the SoS that are initiated by unexpected behaviors of other systems within the SoS. The method is demonstrated using an example of an autonomous vehicle network operating in a partially denied environment with hostile forces present. Using the concept of irrationality initiators, it is possible to identify and prioritize vulnerabilities in the system of interest in the SoS.