Modelling and measuring the operability of interdependent systems and systems of systems: advances in methods and applications

Interdependency is an important consideration in managing systems and systems of systems. Included in this consideration is identifying, representing, and measuring the ripple effects of dependencies between systems and consumers who rely on their products and services. Anticipating these effects enables planners to minimise dependency risks that, if realised, can have cascading impacts on the ability of systems to deliver services. This paper presents advances in modelling interdependent systems by integrating two methods: functional dependency network analysis (FDNA) and the inoperability input-output model (IIM). Their integration enables hierarchical modelling of perturbations to systems at the physical or operational network levels. To highlight the insights gained by integrating FDNA and IIM, a simulated electric power system that feeds a large metropolitan area is presented. This simulated case demonstrates that other consequence measures, such as the inoperability metric presented herein, must be used in conjunction with monetary objectives to generate holistic prioritisation strategies.