Bibliographical details

Building trustworthy (dependable) systems is a major challenge faced by software developers. To this end, various fault tolerance mechanisms have been developed by researchers and used in industry. Unfortunately, more often than not these solutions ignore earlier development phases most importantly, the architecture design to exclusively focus on the implementation instead. This creates a dangerous gap between the requirement to build dependable (and fault tolerant) systems and the failure to address these issues at any stage preceding the implementation step. Software Architecture has been widely accepted as a way to achieve a better software quality while reducing the time and cost of production. While typical architectural specifications model only the normal behaviour of the system, ignoring the abnormal ones, several approaches have recently been developed which break the wrong pattern. The aim of this paper is to survey the existing approaches to architecting fault tolerant systems, offering its readers a clear picture of the state of the art research in this emerging area. This survey is built on developing a twodimensional classification of the existing solutions: the first dimension is based on the traditional software engineering characteristics while the second one uses fault tolerance-related parameters. The paper analyses the major trends and identifies possible directions for future research. About the authors Dr Henry Muccini is an Assistant Professor with Dipartimento di Informatica, University of L'Aquila, Italy. Henry works on software engineering focusing on architectural languages, architecture-based analysis and architecturing wireless sensor networks. More information about henry can be found here web site is www.henrymuccini.com. Alexander (Sascha) Romanovsky is a Professor in the Centre for Software and Reliability, Newcastle University. His main research interests are system dependability, fault tolerance, software architectures, exception handling, error recovery, system structuring and verification of fault tolerance. He received a M.Sc. degree in Applied Mathematics from Moscow State University and a PhD degree in Computer Science from St. Petersburg State Technical University. He was with this University from 1984 until 1996, doing research and teaching. In 1991 he worked as a visiting researcher at ABB Ltd Computer Architecture Lab Research Center, Switzerland. In 1993 he was a visiting fellow at Istituto di Elaborazione della Informazione, CNR, Pisa, Italy. In 1993-94 he was a postdoctoral fellow with the Department of Computing Science, the University of Newcastle upon Tyne. In 1992-1998 he was involved in the Predictably Dependable Computing Systems (PDCS) ESPRIT Basic Research Action and the Design for Validation (DeVa) ESPRIT Basic Project. In 1998-2000 he worked on the Diversity in Safety Critical Software (DISCS) EPSRC/UK Project. Prof Romanovsky was a co-author of the Diversity with Off-TheShelf Components (DOTS) EPSRC/UK Project and was involved in this project in 2001-2004. In 2000-2003 he was in the executive board of Dependable Systems of Systems (DSoS) IST Project. He has been the Coordinator of the Rigorous Open Development Environment for Complex Systems (RODIN) IST Project (2004-2007). He is now the Coordinator of the major FP7 DEPLOY Integrated Project (2008-2012) on Industrial Deployment of System Engineering Methods Providing High Dependability and Productivity. Suggested keywords DEPENDABILITY SOFTWARE ARCHIETCTURES FAULT TOLERANCE