Towards QVA - Quantitative vulnerability assessment: a generic practical model

Within the quest for sound and practical solutions to quantify the vulnerability of critical infrastructures a model is proposed providing, in essence: (i) a two-parameter description and the respective equation of state, for any multicomponent, multiindicator system featuring two states: 'operable' and 'inoperable'; (ii) a division of the two-parameter phase space of the system into 'vulnerability basins'; and (iii) a 0 to 100 'Vulnerability Scale', and the means to measure the respective 'Vulnerability Index', as an operational expression of a 'Quantitative Vulnerability Assessment' (QVA). A method to diagnose the current vulnerability of a complex system featuring large numbers of indicators, both internal and external, as well as to dynamically monitor the time-evolvement of the vulnerability as the indicators change, is demonstrated. A consequent algorithm and its software implementation are introduced. The method, algorithm, and software are generic, and are believed to accommodate a virtually unlimited variety of applications. The notions are inspired by reference frameworks in classical statistical physics such as the Bragg-Williams approximation of the Ising model, feed from the alternative interpretations by Thom and Zeeman, of the stability problem in Systems Theory, and are encouraged by the similar approaches by Hacken, Weidlich and others.