SysML fault modelling in a traffic management system of systems

Systems of systems (SoSs) are vulnerable to faults, for example arising as a result of the distribution and independence of their constituent systems. Our previous work has presented an initial framework for reasoning about faults and fault-tolerant design within an SoS at the architectural level, using a simple example of a single failure. In this paper we present a motivating example of an SoS within which failures of constituent systems (CSs) may lead to a degraded or partial service for the SoS. We discuss a possible extension to our earlier framework to allow an architectural engineer to reason about the fault tolerance of an SoS where CSs contribute negatively or positively towards a goal or an SoS-level failure, and where multiple SoS faults may interact to affect SoS service quality.