Resilient Control Systems Practical Metrics Basis for Defining Mission Impact

'Resilience' describes how systems operate at an acceptable level of normalcy despite disturbances or threats. In this paper we first consider the cognitive, cyber-physical interdependencies inherent in critical infrastructure systems and how resilience differs from reliability to mitigate these risks. Terminology and metrics basis are provided to integrate the cognitive, cyber-physical aspects that should be considered when defining solutions for resilience. A practical approach is taken to roll this metrics basis up to system integrity and business case metrics that establish 'proper operation' and 'impact.' A notional chemical processing plant is the use case for demonstrating how the system integrity metrics can be applied to establish performance, and as well, the effects on the process that roll into the business case.