Download or read book Fault Tolerant Systems written by Israel Koren and published by Elsevier. This book was released on 2010-07-19 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fault-Tolerant Systems is the first book on fault tolerance design with a systems approach to both hardware and software. No other text on the market takes this approach, nor offers the comprehensive and up-to-date treatment that Koren and Krishna provide. This book incorporates case studies that highlight six different computer systems with fault-tolerance techniques implemented in their design. A complete ancillary package is available to lecturers, including online solutions manual for instructors and PowerPoint slides. Students, designers, and architects of high performance processors will value this comprehensive overview of the field. - The first book on fault tolerance design with a systems approach - Comprehensive coverage of both hardware and software fault tolerance, as well as information and time redundancy - Incorporated case studies highlight six different computer systems with fault-tolerance techniques implemented in their design - Available to lecturers is a complete ancillary package including online solutions manual for instructors and PowerPoint slides

Download or read book Fault Tolerant Real Time Systems written by Stefan Poledna and published by Springer Science & Business Media. This book was released on 2007-11-23 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Real-time computer systems are very often subject to dependability requirements because of their application areas. Fly-by-wire airplane control systems, control of power plants, industrial process control systems and others are required to continue their function despite faults. Fault-tolerance and real-time requirements thus constitute a kind of natural combination in process control applications. Systematic fault-tolerance is based on redundancy, which is used to mask failures of individual components. The problem of replica determinism is thereby to ensure that replicated components show consistent behavior in the absence of faults. It might seem trivial that, given an identical sequence of inputs, replicated computer systems will produce consistent outputs. Unfortunately, this is not the case. The problem of replica non-determinism and the presentation of its possible solutions is the subject of Fault-Tolerant Real-Time Systems: The Problem of Replica Determinism. The field of automotive electronics is an important application area of fault-tolerant real-time systems. Systems like anti-lock braking, engine control, active suspension or vehicle dynamics control have demanding real-time and fault-tolerance requirements. These requirements have to be met even in the presence of very limited resources since cost is extremely important. Because of its interesting properties Fault-Tolerant Real-Time Systems gives an introduction to the application area of automotive electronics. The requirements of automotive electronics are a topic of discussion in the remainder of this work and are used as a benchmark to evaluate solutions to the problem of replica determinism.

Download or read book Real Time Systems written by Hermann Kopetz and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: 7. 6 Performance Comparison: ET versus TT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 7. 7 The Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Points to Remember . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Chapter 8: The Time-Triggered Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 8. 1 Introduction to Time-Triggered Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 8. 2 Overview of the TTP/C Protocol Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 8. 3 TheBasic CNI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Internal Operation of TTP/C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 8. 4 8. 5 TTP/A for Field Bus Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Review Questions and Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Chapter 9: Input/Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 9. 1 The Dual Role of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 9. 2 Agreement Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 9. 3 Sampling and Polling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 9. 4 Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 9. 5 Sensors and Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 9. 6 Physical Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Chapter 10: Real-Time Operating Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 10. 1 Task Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 10. 2 Interprocess Communication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 10. 3 Time Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 10. 4 Error Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10. 5 A Case Study: ERCOS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 Bibliographic Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Chapter 11: Real-Time Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 11. 1 The Scheduling Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 11. 2 The Adversary Argument. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 11. 3 Dynamic Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 x TABLE OF CONTENTS 11. 4 Static Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Bibliographic Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Review Questions and Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Chapter 12: Validation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 12. 1 Building aConvincing Safety Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 12. 2 Formal Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 12. 3 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Download or read book Research Anthology on Architectures Frameworks and Integration Strategies for Distributed and Cloud Computing written by Management Association, Information Resources and published by IGI Global. This book was released on 2021-01-25 with total page 2700 pages. Available in PDF, EPUB and Kindle. Book excerpt: Distributed systems intertwine with our everyday lives. The benefits and current shortcomings of the underpinning technologies are experienced by a wide range of people and their smart devices. With the rise of large-scale IoT and similar distributed systems, cloud bursting technologies, and partial outsourcing solutions, private entities are encouraged to increase their efficiency and offer unparalleled availability and reliability to their users. The Research Anthology on Architectures, Frameworks, and Integration Strategies for Distributed and Cloud Computing is a vital reference source that provides valuable insight into current and emergent research occurring within the field of distributed computing. It also presents architectures and service frameworks to achieve highly integrated distributed systems and solutions to integration and efficient management challenges faced by current and future distributed systems. Highlighting a range of topics such as data sharing, wireless sensor networks, and scalability, this multi-volume book is ideally designed for system administrators, integrators, designers, developers, researchers, academicians, and students.

Download or read book Responsive Computer Systems Steps Toward Fault Tolerant Real Time Systems written by Donald Fussell and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Responsive Computer Systems: Steps Towards Fault-Tolerant Real-Time Systems provides an extensive treatment of the most important issues in the design of modern Responsive Computer Systems. It lays the groundwork for a more comprehensive model that allows critical design issues to be treated in ways that more traditional disciplines of computer research have inhibited. It breaks important ground in the development of a fruitful, modern perspective on computer systems as they are currently developing and as they may be expected to develop over the next decade. Audience: An interesting and important road map to some of the most important emerging issues in computing, suitable as a secondary text for graduate level courses on responsive computer systems and as a reference for industrial practitioners.

Download or read book Software Implemented Hardware Fault Tolerance written by Olga Goloubeva and published by Springer Science & Business Media. This book was released on 2006-09-19 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the theory behind software-implemented hardware fault tolerance, as well as the practical aspects needed to put it to work on real examples. By evaluating accurately the advantages and disadvantages of the already available approaches, the book provides a guide to developers willing to adopt software-implemented hardware fault tolerance in their applications. Moreover, the book identifies open issues for researchers willing to improve the already available techniques.

Download or read book Hardware and Software Architectures for Fault Tolerance written by Michel Banatre and published by Springer Science & Business Media. This book was released on 1994-02-28 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fault tolerance has been an active research area for many years. This volume presents papers from a workshop held in 1993 where a small number of key researchers and practitioners in the area met to discuss the experiences of industrial practitioners, to provide a perspective on the state of the art of fault tolerance research, to determine whether the subject is becoming mature, and to learn from the experiences so far in order to identify what might be important research topics for the coming years. The workshop provided a more intimate environment for discussions and presentations than usual at conferences. The papers in the volume were presented at the workshop, then updated and revised to reflect what was learned at the workshop.

Download or read book Software Engineering of Fault Tolerant Systems written by Patrizio Pelliccione and published by World Scientific. This book was released on 2007 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: When architecting dependable systems, fault tolerance is required to improve the overall system robustness. Many studies have been proposed, but the solutions are usually commissioned late during the design and implementation phases of the software life-cycle (e.g., Java and Windows NT exception handling), thus reducing the error recovery effectiveness. Since the system design typically models only normal behaviors of the system while ignoring exceptional ones, the generated system implementation is unable to handle abnormal events. Consequently, the system may fail in unexpected ways due to some faults. Researchers have advocated that fault tolerance management during the entire life-cycle improves the overall system robustness and that different classes of exceptions must be identified for each identified phase of software development, depending on the abstraction level of the software system being modeled. This book builds on this trend and investigates how fault tolerance mechanisms can be used when engineering a software system. New problems will arise, new models are needed at different abstraction levels, methodologies for mode driven engineering of such systems must be defined, new technologies are required, and new validation and verification environments are necessary.

Download or read book Fault tolerant Computer System Design written by Dhiraj K. Pradhan and published by Prentice Hall. This book was released on 1996 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the ten years since the publication of the first edition of this book, the field of fault-tolerant design has broadened in appeal, particularly with its emerging application in distributed computing. This new edition specifically deals with this dynamically changing computing environment, incorporating new topics such as fault-tolerance in multiprocessor and distributed systems.

Download or read book Resource Management in Real time Systems and Networks written by C. Siva Ram Murthy and published by MIT Press. This book was released on 2001 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the concepts and state-of-the-art research developments of resource management in real-time systems and networks. Real-time systems and networks are of increasing importance in many applications, including automated factories, telecommunication systems, defense systems, and space systems. This book introduces the concepts and state-of-the-art research developments of resource management in real-time systems and networks. Unlike other texts in the field, it covers the entire spectrum of issues in resource management, including task scheduling in uniprocessor real-time systems; task scheduling, fault-tolerant task scheduling, and resource reclaiming in multiprocessor real-time systems; conventional task scheduling and object-based task scheduling in distributed real-time systems; message scheduling; QoS routing; dependable communication; multicast communication; and medium access protocols in real-time networks. It provides algorithmic treatments for all of the issues addressed, highlighting the intuition behind each algorithm and giving examples. The book also includes two chapters of case studies.

Download or read book Design And Analysis Of Reliable And Fault tolerant Computer Systems written by Mostafa I Abd-el-barr and published by World Scientific. This book was released on 2006-12-15 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covering both the theoretical and practical aspects of fault-tolerant mobile systems, and fault tolerance and analysis, this book tackles the current issues of reliability-based optimization of computer networks, fault-tolerant mobile systems, and fault tolerance and reliability of high speed and hierarchical networks.The book is divided into six parts to facilitate coverage of the material by course instructors and computer systems professionals. The sequence of chapters in each part ensures the gradual coverage of issues from the basics to the most recent developments. A useful set of references, including electronic sources, is listed at the end of each chapter./a

Download or read book Fault Tolerant Systems written by Israel Koren and published by Morgan Kaufmann. This book was released on 2020-09-01 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fault-Tolerant Systems, Second Edition, is the first book on fault tolerance design utilizing a systems approach to both hardware and software. No other text takes this approach or offers the comprehensive and up-to-date treatment that Koren and Krishna provide. The book comprehensively covers the design of fault-tolerant hardware and software, use of fault-tolerance techniques to improve manufacturing yields, and design and analysis of networks. Incorporating case studies that highlight more than ten different computer systems with fault-tolerance techniques implemented in their design, the book includes critical material on methods to protect against threats to encryption subsystems used for security purposes. The text's updated content will help students and practitioners in electrical and computer engineering and computer science learn how to design reliable computing systems, and how to analyze fault-tolerant computing systems. - Delivers the first book on fault tolerance design with a systems approach - Offers comprehensive coverage of both hardware and software fault tolerance, as well as information and time redundancy - Features fully updated content plus new chapters on failure mechanisms and fault-tolerance in cyber-physical systems - Provides a complete ancillary package, including an on-line solutions manual for instructors and PowerPoint slides

Download or read book Dependable Embedded Systems written by Jörg Henkel and published by Springer Nature. This book was released on 2020-12-09 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Open Access book introduces readers to many new techniques for enhancing and optimizing reliability in embedded systems, which have emerged particularly within the last five years. This book introduces the most prominent reliability concerns from today’s points of view and roughly recapitulates the progress in the community so far. Unlike other books that focus on a single abstraction level such circuit level or system level alone, the focus of this book is to deal with the different reliability challenges across different levels starting from the physical level all the way to the system level (cross-layer approaches). The book aims at demonstrating how new hardware/software co-design solution can be proposed to ef-fectively mitigate reliability degradation such as transistor aging, processor variation, temperature effects, soft errors, etc. Provides readers with latest insights into novel, cross-layer methods and models with respect to dependability of embedded systems; Describes cross-layer approaches that can leverage reliability through techniques that are pro-actively designed with respect to techniques at other layers; Explains run-time adaptation and concepts/means of self-organization, in order to achieve error resiliency in complex, future many core systems.

Download or read book Distributed Real Time Systems written by K. Erciyes and published by Springer. This book was released on 2019-07-23 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: This classroom-tested textbook describes the design and implementation of software for distributed real-time systems, using a bottom-up approach. The text addresses common challenges faced in software projects involving real-time systems, and presents a novel method for simply and effectively performing all of the software engineering steps. Each chapter opens with a discussion of the core concepts, together with a review of the relevant methods and available software. This is then followed with a description of the implementation of the concepts in a sample kernel, complete with executable code. Topics and features: introduces the fundamentals of real-time systems, including real-time architecture and distributed real-time systems; presents a focus on the real-time operating system, covering the concepts of task, memory, and input/output management; provides a detailed step-by-step construction of a real-time operating system kernel, which is then used to test various higher level implementations; describes periodic and aperiodic scheduling, resource management, and distributed scheduling; reviews the process of application design from high-level design methods to low-level details of design and implementation; surveys real-time programming languages and fault tolerance techniques; includes end-of-chapter review questions, extensive C code, numerous examples, and a case study implementing the methods in real-world applications; supplies additional material at an associated website. Requiring only a basic background in computer architecture and operating systems, this practically-oriented work is an invaluable study aid for senior undergraduate and graduate-level students of electrical and computer engineering, and computer science. The text will also serve as a useful general reference for researchers interested in real-time systems.

Download or read book Formal Techniques in Real Time and Fault Tolerant Systems written by Werner Damm and published by Springer. This book was released on 2003-06-30 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of FTRTFT 2002, the International S- posium on Formal Techniques in Real-Time and Fault-Tolerant Systems, held at the University of Oldenburg, Germany, 9–12 September 2002. This sym- sium was the seventh in a series of FTRTFT symposia devoted to problems and solutions in safe system design. The previous symposia took place in Warwick 1990, Nijmegen 1992, Lub ̈ eck 1994, Uppsala 1996, Lyngby 1998, and Pune 2000. Proceedings of these symposia were published as volumes 331, 571, 863, 1135, 1486, and 1926 in the LNCS series by Springer-Verlag. This year the sym- sium was co-sponsored by IFIP Working Group 2.2 on Formal Description of Programming Concepts. The symposium presented advances in the development and use of formal techniques in the design of real-time, hybrid, fault-tolerant embedded systems, covering all stages from requirements analysis to hardware and/or software - plementation. Particular emphasis was placed on UML-based development of real-time systems. Through invited presentations, links between the dependable systems and formal methods research communities were strengthened. With the increasing use of such formal techniques in industrial settings, the conference aimed at stimulating cross-fertilization between challenges in industrial usages of formal methods and advanced research. Inresponsetothecallforpapers,39submissionswerereceived.Eachsubm- sion was reviewed by four program committee members assisted by additional referees. At the end of the reviewing process, the program committee accepted 17 papers for presentation at the symposium.

Download or read book Fault Tolerance in Distributed Systems written by Pankaj Jalote and published by Prentice Hall. This book was released on 1994 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fault tolerance is an approach by which reliability of a computer system can be increased beyond what can be achieved by traditional methods. Comprehensive and self-contained, this book explores the information available on software supported fault tolerance techniques, with a focus on fault tolerance in distributed systems.

Download or read book Dependable Computing for Critical Applications written by Algirdas Avizienis and published by Springer. This book was released on 2012-02-12 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: The International Working Conference on Dependable Computing for Critical Applications was the first conference organized by IFIP Working Group 10. 4 "Dependable Computing and Fault Tolerance", in cooperation with the Technical Committee on Fault-Tolerant Computing of the IEEE Computer Society, and the Technical Committee 7 on Systems Reliability, Safety and Security of EWlCS. The rationale for the Working Conference is best expressed by the aims of WG 10. 4: " Increasingly, individuals and organizations are developing or procuring sophisticated computing systems on whose services they need to place great reliance. In differing circumstances, the focus will be on differing properties of such services - e. g. continuity, performance, real-time response, ability to avoid catastrophic failures, prevention of deliberate privacy intrusions. The notion of dependability, defined as that property of a computing system which allows reliance to be justifiably placed on the service it delivers, enables these various concerns to be subsumed within a single conceptual framework. Dependability thus includes as special cases such attributes as reliability, availability, safety, security. The Working Group is aimed at identifying and integrating approaches, methods and techniques for specifying, designing, building, assessing, validating, operating and maintaining computer systems which should exhibit some or all of these attributes. " The concept of WG 10. 4 was formulated during the IFIP Working Conference on Reliable Computing and Fault Tolerance on September 27-29, 1979 in London, England, held in conjunction with the Europ-IFIP 79 Conference. Profs A. Avi~ienis (UCLA, Los Angeles, USA) and A.