Critical Infrastructures (CI) are central systems for ensuring life and services to citizens. They are thus the technological objects at the vertex of the nation’s priority scale, as far as protection issues are concerned.
CIs are excellent metaphors of Complex Systems (CS). Their structure is a composition of technological elements; their mutual interdependency and their dependence on human-controlled chains lead them to contain all the issues and properties which "define" a Complex System. Relationships between components are non-linear,contain feedback loops, are open systems and, as such, work far fromequilibrium; they are also constituted by complex elements.
CS has allowed to tackle, in the last ten years, the analysis of a large variety of systems of different origins (technological, biological, social and others), as shown by the huge amount of scientific literature produced in these years. Also major critical infrastructures (such as electrical grids [2-4], communication networks such as routes and railways [5,6], information networks such as the Internet [7-8] etc.) have been analyzed, particularly under the standpoint of their network’s topology. Most CIs can be ascribed to the class of systems growing with no external supervision and, as such, their behavior can be considered as indistinguishable from that pertaining to "natural" systems which evolve under the effect of some sort of selective pressure. Aside to basic questions aimed at understanding growth mechanisms, robustness, vulnerability, there is still anumber of questions to be addressed by static and dynamic models of CIs

• the relationship between topological structure and function
• the assessment of effective "functional" vulnerability
• the exploration of the functional phase space to detect phase transition and/or critical points
• fast and reliable decision support
• reliable reconfigurability

The technological scenario of CIs is further complicated by the presence of a peculiar feature which accomunate these objects: their mutual interdepedency. This term indicates the fact than, more than ever, CIs cannot be thought as stand-alone entities but they are mutually inter-dependent in the sense that a perturbation occurring on one of them might have (small or large) repercussion on the others. These feedback effects lead the study of emergent properties of these systems even more intriguing. The emergence of new effects might be thus associated also to agencies which lie outside the realm of definition and functioning of a given CI and related to misfunctioning in other networks (like, e.g., the catastrophic effects induced by a prolonged electrical blackout on communication networks, whose resulting fault inhibits, in turn, theavailability of a communication network allowing tele-controlling and thus needed to perform the necessary actions for restoring the electrical grid). These "perverse" feedbacks are at the origin of the so-called "cascade effects" recorded and analysed during recent large-scale blackouts, which affected several western countries in recent years (Italian and US blackouts in 2003, Germany-France-Italy blackouts in 2006 and other minor regional events).

There are a number of relevant technological questions which arise from stakeholders who operate major CIs such as electrical grids, communication networks but also transport networks. They are related both to the intrinsic mechanisms ruling the normal activity of these networks and to the exogenous agencies leading to (usually non-linear) perturbation effects.

The main aim of the Satellite Workshop is to establish a link betweenthe basic science community of CS with a management counterpart made of technological operators who must analyse and care for the efficiency of large national CIs.

The advent of new technological scenario (like that described caused by micro-generation for the power grid) opens the way to more deep reflection on the ideas and the methods to be used to develop new tools for the control andthe management of CIs. Indeed, the EU FP6 programme hosted a number of projects aimed at definitely bridging the gap between basic science and technologicaloperations, in this field. Among them, the IRRIIS project, whose scientific goals totally complies with the intents of the proposed Workshop. In fact, IRRIIS is an Integrated Project grouping the major institutions and some european CI stakeholders; it is aimed at increasing dependability, survivability and resilience of these information-based infrastructures through, among others, the development of a "Middleware Improved Technology", a collection of software components, which facilitates IT-based communication between different infrastructures and different infrastructure providers, by supporting recovery actions and increasing service stability in case of critical situations. In this contest, IRRIIS is going to stimulate the interaction between the scientific and the technological communities around the problems opened by the complexity of CIs.
Actions and programmes devoted to these problems are also forecast for FP7. The proposed Workshop would also provide a dissemination forum to let the scientific community aware of these problems and to stimulate the creation of scientific and technological groups ready to take the challenges.

This one-day Workshop, structured around a few Invited Speakers, will present the major problems and the on-going challenges in this area. They will be part of EU and non-EU consortia which are involved in producing new instruments for the moderncontrol of CIs, many of them based (or using) CS ideas and methods. We will also provide an opportunity to other scientists to present original works. A further purpose of the Workshop is also to establish a two-way connection between Science and Technology:

• one one side, technology and CI operations will present their problems to the CS scientific community
• on the other side, scientific community, which has been attracted by these problems, might have the opportunity to explain, to a wider audience, the results of their analysis which might open new frontiers in the field of analysis and control of CIs.

Among the scientific themes which would be touched by the Workshop we will quote, hereafter, a (non exhaustive) lists topics:

• Topological properties of critical infrastructures networks; this subject has been among those used as astarting point to introduce CS issues into CI analysis. To date, many different CI worldwide have been analysed (electrical grids, the internet, social andeconomic networks etc.); these studies allowed to achieve significant results,on both basic science and technological aspects of CIs. Topological analysis has been also coupled to vulnerability assessment of CIs, with significant results.

• Modelling & simulation of critical infrastructures; this subject is particularly relevant as there is a wide tendency to couple static (topological) to dynamical models of functional networks to produce "behavioural" models of CIs which might provide also qualitative information of their functioning, etsblish the onset of critical or emergent phenomena etc.

• Phase transitions on complex infrastructures; this is a territory, typical of theoretical physics, which assumes a paramount relevance in the area of analysis and control of CIs. Phase transitions (like, e.g., congestions in TLC networks or jams in traffic networks) are related to the issue of the "intrinsic" technological limits of CIs, whose causes must be understood in order to prevent their occurrence.

• Modelling interaction between complex systems; this is a "hot" topic which resumes the to date problem which should be faced, which leads CI to enhance their level of criticality with respect to citizen’s life. A comprehensive modelling of large scale CIs is needed; basic science should be encouraged to deploy all its "reductionist" capability to attempt to give an answer to that need.

• Emerging behaviour caused by infrastructure's interdependency; this issue can be tackled by combining dynamical models of CIs and the modelling of CI’s interactions. This is also a theme which could have a major technological interest for CI’s managers.

• Real systems scenarios; this should represent the "technological" viewpoint, where stakeholders should provide the up-date of the methods and the tolls which are currently used for the management of the operations on large scale CIs and present which are the type of "crisis" which these tools are called to solve.

• Trust and information exchange between infrastructures; this topic is critical since it provides the input to models and simulators that analyze or represent the behavior of the infrastructures.

[1] S. Boccaletti et al., Phys. Reports 424 (2006) 175.
[2] R. Albert, I. Albert, G.L. Nakarano, Phys.Rev.E 69 (2004) 025103(R).
[3] V. Rosato, F. Tiriticco, Europhys. Lett. 66 (2004) 471.
[4] F. Tiriticco, S. Bologna, V. Rosato, Electr. Power Syst. Res. 77 (2007) 99.
[5] D. Helbing, Rev. Mod. Phys. 73 (2001) 1067.
[6] C.J. Goodman et al., in IEEE Int. Conf. On Development in Mass Transit Systems 1998 (Conf. Publ.No.453)
[7] R. Pastor-Satorras, A. Vespignani, "Evolution and Structure of theInternet: a Statistical Physics Approach"
(Cambridge University Press,Cambridge, 2004).
[8] S-H. Yook, H. Jeong, A-L. Barabasi, Proc. Nat. Ac. Science USA 99 (2002) 13382.

• Prof. Ravi K. Iyer, George and Ann Fisher Distinguished Professor and Director of Coordinated Science Laboratory, University of Illinois, Urbana IL 61801
• Dr. Vito Latora, Assistant Professor, Dipartimento di Fisica, Universita' di Catania (Italy)
• Dr. Jean-Claude Laprie, Laboratoire d'Analyse et d'Architecture des Systèmes, Toulouse (France)
• Dr. Walter Willinger, AT&T Labs. Inc.-Research, 180 Park Avenue, Florham Park, NJ, 07932 (USA)

Critical Infrastructures (CI) are central systems for ensuring life and services to citizens. They are thus at the vertex of the nation’s priority scale. CIs are excellent metaphors of Complex Systems (CS). Their structure, composition of technological elements, their mutual interdependency, their dependence on human-controlled chains lead them to contain all the issues and properties which "define" a Complex System. Relationships between componentsare non-linear, contain feedback loops, they are open systems and, as such,works far from equilibrium, are constituted by complex elements The present Satellite Workshop is organized by the EU Integrated Project IRRIIS (Integrated Risk Reduction of Information-based Infrastructure Systems). The main aim is to bring to the attention of a wide audience, the open problems concerning the analysis and the control of CIs, with the aim of triggering interest and getting ideas for the development of new solutions and new tools enabling the reach of a better control and understanding of the effects emerging from their complexity. The ultimate goal is to realize new tools which will allow to reduce faults and effects of faults, to lead CI less vulnerable and more robust, to understand interdependencies and to sustain operator in the decision chains during crisis events. The Workshops would also attempt to contribute to the close-up the basic-science community with that of operators in the area of CI analysis and control and to foster a new deal of collaboration, also in view of common interests comprised in the priority themes of EU FP7. The one-day Workshop will be structured with talks of invited speakers, which will introduce the technological issues of CI analysis and control and of a number of technical presentations which will highlight how CS ideas and methods could be relevant in this context. We thus invite the CS community to present work on the following topics (non-exhaustive list):

• topological properties of critical infrastructures networks
• modelling &simulation of critical infrastructures
• phase transitions on complex infrastructures
• modelling interaction between complex systems
• emerging behaviour caused by infrastructure's interdependency
• real systems scenarios

Contributions which will not be selected for oral presentation will be invited to be presented in a poster session hosted by the Workshop. Both oral and poster presentations will be then published (according to the usual rules) in a special issue in one of the international journals selected by ECCS07.

The Workshop is partly funded by GIACS (a EU FP6 Coordinated Action) which will allow to grant students (post-graduate and Ph.D. students) to attend the Conference.