Area method used in the evaluation of resilience implementation approaches in system of systems

System of systems (SoS), like transportation systems and combat systems, is integrated by a set of independently operating systems that interact with each other to provide an end-to-end capability, which cannot be achieved by individual systems. Resilience is the ability of an SoS to recover to a desired performance level after disruptive events. Even though many measures have been proposed to evaluate resilience, there is no one general metric that can be used in all situations. Given that what we actually need is the performance process with time, this paper presents an area method to evaluate resilience by calculating the area below the performance curve after disruption. Meanwhile, we propose the SoS operating time, combined with the area method, to identify which of the recovered performance levels and the recovery speeds is more important according to different situations. Finally, the proposed research enables us to evaluate resilience implementation approaches and select the best one.