## 3 Resilience
### Disturbance Event Phases  
Resilience evaluation is indispensable for decision support, aiming to quantify the efficacy of preparedness expenses and plans. A practical preparedness blueprint enhances the stability of critical infrastructure in the wake of a disruptive event. Numerous models and measures have been devised to gauge the performance and service of smart systems, aiding in the design, upkeep, and enhancement of overall resilience. Nevertheless, resilience is a complex concept, challenging to tackle by examining just one specific capability. A comprehensive approach to tackle the intricacies of resilience necessitates the creation of sophisticated measures that scrutinize key resilience characteristics--primarily absorptive, adaptive, and restorative capabilities. These attributes must be evaluated in the context of different phases of a disruptive event, considering the unique conditions and challenges each phase presents. Each assessed attribute represents a component of the system's response to disruptions, offering insights into its ability to absorb shock, adapt to changing conditions, and restore its functionality. Once these assessments are made, they can be synthesized into a singular, unified resilience metric that encapsulates the system's overall resilience. The refinement of this unified resilience metric can be further achieved by transitioning the phases of disturbance events into weighted points. This process allows the contribution of each phase to the overall resilience to be quantified and compared. Such a method facilitates independent experts in delineating estimates for limit values, thereby adding an additional layer of precision to the resilience metric. This comprehensive and robust resilience metric not only encapsulates the system's resilience across various phases of a disruptive event but also provides a quantifiable means to compare and improve resilience across different systems or configurations. Thus, it serves as a crucial tool for decision makers in enhancing the resilience of critical infrastructures. * **Risk comprehension:** Applicable prior to the adverse event, this phase underscores potential emerging risks (ERs) and involves early detection. For example, what might the _adverse event_ entail? How can we gather more information and context about the risk or hazards? * **Anticipation and preparation:** This phase involves devising preparation and proactive evolution plans. For instance, what outcomes should we anticipate? * **Absorptive capacity/withstand:** Absorptive capacity pertains to the system's ability to mitigate the negative implications caused by disruptive events and minimize their impact. An exemplification of this phase is enhancing robustness to improve system redundancy, which offers an alternate means for the system to operate. * **Restorative capacity/recovery:** Restorative capacity concerns the infrastructure's ability to be enhanced by external interventions during the recovery period. For instance, implementing real-time monitoring operations (e.g., Supervisory Control and Data Acquisition system or SCADA for most infrastructures) bolsters the infrastructure's restorative capability. It allows for the automated detection of disruptive events, which is crucial in minimizing the total disruption time. * **Absorption/withstand:** This phase corresponds to the actions during the initial phase of the event and should include vulnerability analysis and potential consequences. For example, how steep is the absorption curve and how far below will it dip? * **Adaptation/learning:** Adaptive capacity refers to the infrastructure's ability to adjust to disruptive events within its self-organization skills to minimize outcomes. It represents the remarkable ability of the infrastructure to improve itself during the recovery period. Several approaches to quantify resilience have been introduced recently.