Proceedings of the 4th International Workshop on Theoretical Aspects of Dynamic Distributed Systems (TADDS 2012)

General Chairs Lélia Blin, University of Evry and LIP6 University Curie, France Yann Busnel, University of Nantes, LINA, France Program Commitee Roberto Baldoni, University of Rome "La Sapienza", Italy Lélia Blin, University of Evry and LIP6 University Curie, France Yann Busnel, University of Nantes, LINA, France Yuval Emek, ETH, Switzerland Pascal Felber, University of Neuchatel, Switzerland Alexander Shvartsmam, University of Connecticut, USAInternational audienceThe Workshop on Theoretical Aspects of Dynamic Distributed Systems, TADDS, has its focus on the dynamic aspects of distributed systems, encompassing systems in existence today and looking into the future development and deployment of dynamic distributed systems, with sound theoretical foundations in mind. The first TADDS workshop was held in Elche, Spain on September 26, 2009, and the second TADDS workshop was held in Cambridge, Massachusetts on September 12, 2010. The third TADDS workshop was held in Rome, Italy on September 19, 2011, co-located with the International Symposium on Distributed Computing, DISC 2012. This edition of the 4th TADDS workshop also held in Rome, Italy on December 17, 2012, co-located with the International Conference On Principles Of DIstributed Systems, OPODIS 2012. Distributed systems are ubiquitous in modern computing. The nature of distributed systems is evolving in response to application requirements, and the advent of new classes of applications and technologies, such as VANET, Airborne Networks, Smart Environments, P2P, Internet Supercomputing, and distributed cloud services, are radically changing the way we think about them. These systems are characterized by dynamic arrival and departure of participating entities and normally it may not be possible to assume anything about the universe of participants, their identities, capabilities, or reliability. In such settings, planned and unexpected perturbations in the computing medium are the norm and not the exception. It is imperative for applications to cope with such dynamic changes while maintaining their correctness. In managing dynamic systems one cannot rely on a centralized management schemes that can either become a bottleneck or simply be unfeasible due to the size of the system. Instead, the processes need to behave autonomously, employing some form of self-management. In a dynamic distributed system each process must autonomously decides to locally run a component of a distributed application (i.e., when joining and leaving the system). Here the system and/or its components do not start with a known and pre-defined setting, and a "nice" manageable system model assumptions either cannot be guaranteed or do not last for long. It is also important to have measurable metrics and notions of efficiency that would allow one to analyse formally the performance and fault tolerance of dynamic systems when one cannot rely on the initial parameterization and a priori knowledge to characterize their behaviour. Understanding the fundamentals of how to master this dynamic dimension is of primary importance to design of robust, dependable, and predictable distributed systems, and is the raison d'être of the workshop. The Program Committee of TADDS 2012 consisted of Roberto Baldoni, University of Rome "La Sapienza", Italy, Lélia Blin (Co-Chair), University of Evry and LIP6 University Curie, France, Yann Busnel (Co-chair), University of Nantes, LINA, France, Yuval Emek, ETH, Switzerland, Pascal Felber, University of Neuchatel, Switzerland and Alexander Shvartsmam, University of Connecticut, USA. The workshop proceedings consisted of the introductory motivation presented by the organizers, two invited lectures, and five contributed presentations. The invited lecture was delivered by Amos Korman (LIAFA, CNRS, Paris, France), titled "Theoretical Distributed Computing meets Biology" and Dariusz R. Kowalski (University of Liverpool, UK), titled "Communication and privacy in dynamic message-passing systems". The five contributed presentations were based on the papers submitted to the workshop. Each paper was reviewed by at least three members of the Program Committee, and feedback was provided to the authors to help them improve the presentation. The proceedings of the workshop appear in the ACM Digital Library. The organizers are confident that the workshop will motivate further concerted study and analysis of dynamic distributed systems. Lélia Blin & Yann Busnel LIP6 - Université Pierre et Marie Curie Université Evry Val d'Essonne, France LINA / Computer Sciences Department Université de Nantes, Franc