An Agent Based Simulator for Critical Interdependent Infrastructures

The increasing relevance of the technological infrastructures (energy, communication, water supply, transportation, etc.) on our life imposes great attention about their protection. These infrastructures are complex networks, geographically dispersed and can be defined as non-linear systems that interact both among themselves, and with their human owners, operators and users [1]. Moreover, the presence of an increasing number of interdependencies among them has dramatically augmented the complexity of the whole system and, at the same time, has increased its vulnerability. Indeed, due to the tight coupling showed by these infrastructures, an accidental or malicious failure in one of them may easily spread across the networks amplifying its negative consequences and affecting remote (from geographical and/or logical point of view) users. All of this requires to understand the behaviour of the system of systems composed by the different interdependent infrastructures, as stressed also in [2]. Unfortunately this is a very challenging task because “the conventional mathematical methodologies that underpin today’s modelling, simulation and control paradigms are unable to handle the complexity and interconnectedness of these critical infrastructures” as stressed in [1]. However, due to the relevance of the topics, many authors have proposed modelling and simulation techniques devoted to the study of this class of systems [3]. In the literature we find, substantially, two main classes of modelling approaches: Interdependencies Analysis and System Analysis. The first one encompasses some qualitative approaches used to help analysts to identify critical infrastructures and is devoted to better emphasize their interdependencies. On the other side, System Analysis modelling techniques are simulation-intensive approaches able to discover hidden interdependencies and to generate (more or less precise) crisis scenarios. These latter approaches suffer, beside the problem of defining appropriate models, to the difficulties of acquiring detailed quantitative information about each infrastructure. Indeed, the more detailed is a model, the greater the number of numeric parameters it encompasses. Some of them, moreover, may be considered sensitive information and infrastructure stakeholders appear generally very reluctant to their disclosure. To overcome these difficulties we have developed CISIA (Critical Infrastructure Simulation by Interdependent Agents). It represents a sort of hybrid approach which, on the bases of the mostly qualitative information elicited from infrastructures stakeholders, is able to set up a (rather sophisticated) fault propagation simulation. More specifically, the simulator is developed using an Agent Based modelling paradigm where the dynamic of each agent is described via Fuzzy Logic quantities in order to take into account the uncertainties that characterize our knowledge about these infrastructures and to facilitate interaction with infrastructures stakeholders.