The Complexity Science Approach vs. the Simulative Approach

Introduction

The major objective of this Chapter is to investigate the pros and cons to facilitate the choice between the mainstream lines of research in Critical Information Infrastructure Protection. While Complexity inspired models tend to capture the general process, simulations tend instead to replicate the phenomena in all its details, as an effort towards a full representation of the interactions among all parts of a Critical Information Infrastructure (CII) by means of a local description of the elementary components, closely linked through specific relations exploiting several existing emulation tools or ad hoc tools at different levels of abstraction. Among them it is worth mentioning the Event Driven approach, the Federative Simulation approach, the Supply/Demand System approach, and the I/O Models (Leontief based) approaches. The mutual dependence relations may be deterministic or stochastic, represented by mathematical expressions, software agents or complete software emulators of a particular application domain. A number of indications and recent findings will be given and summarized at the end of the Chapter. They pertain to the choice of the most suitable model to simulate depending on the available data, the granularity level of the simulation, the identification of the couplings among the objects, the limitations to the linear and linearized simulation models as well as the limitations due to node dynamical complexity in complex networks and the tendency of all large infrastructures toward a self-organizing criticality (SOC) behavior. The target audience of this Chapter has a basic knowledge of the ICT, power and transportation infrastructures. A mathematical background in dynamical systems, notions of informatics, graph theory, programming would be useful, but by no means mandatory, as the major ideas will be explained plainly and without heavy mathematical notations for the sake of readability.