Safety-critical systems are found in almost every sector of industry. Faults in these systems will result in a breach of safe operating conditions and exposure to the possible risk of major loss of life or catastrophic damage to plant, equipment or the environment. An understanding of the basis for the functioning of these systems is therefore vital to all involved in their operation. In particular, the interaction of the disciplines of software engineering, safety engineering, human factors and safety management is a total process whose entirety is not widely understood by those working in any of the individual fields. This book will redress that problem by providing an introduction to each constituent part with a cohesive structure and overview of the whole subject. It will be of interest to engineers, managers, students and anyone with responsibilities in these areas.

Improvements in System Safety contains the full complement of papers presented at the sixteenth annual Safety-critical Systems Symposium, held at Bristol, UK, in February 2008.

The Symposium is for engineers, managers and academics in the field of safety, across all industry sectors, and so the papers included in this volume offer a wide-ranging coverage of major safety issues as well as a good blend of academic research and industrial experience. They include discussions of some of the most recent developments in the field.

The first paper reflects a tutorial on The Safety Case held on the first day of the Symposium. The subsequent 14 papers are presented under the headings of the Symposium 's sessions: Themes Reprised from SSS 07; The Safety Case; Safety Culture; Human Factors; Achieving and Improving System Safety; Safety and Risk Analysis.

This book will be of interest to both academics and practitioners working in the safety-critical systems arena.

The Safety of Systems contains the invited papers presented at the fifteenth annual Safety-critical Systems Symposium, held at Bristol, UK in February 2007. The papers included in this volume cover a broad spectrum of important safety issues. They provide a combination of industrial experience and recent developments, and are presented under a variety of headings.

Developments in Risk-based Approaches to Safety contains the invited papers presented at the Fourteenth annual Safety-critical Systems Symposium, held at Bristol, UK in February 2006.

The papers included in this volume address the most critical topics in the field of safety-critical systems. The focus this year, considered from various perspectives, is on recent developments in risk-based approaches. Subjects discussed include innovation in risk analysis, management risk, the safety case, software safety, language development and the creation of systems for complex control functions.

Papers provide a mix of industrial experience and academic research results and are presented under the headings: Tutorial, New Approaches to Risk Assessment, Experience of Developing Safety Cases, Management Influence on Safety, Software Safety, New Technologies in Safety-critical Systems, Adding Dimensions to Safety Cases.

Constituents of Modern System-safety Thinking contains the invited papers presented at the Thirteenth annual Safety-critical Systems Symposium, held at Southampton, UK in February 2005.

The papers included in this volume bring together topics that are of the utmost importance in current safety thinking. The core of modern safety thinking and practice is a risk-based approach, and this is not only a common thread running throughout the papers, but is also explored in two of them. Other themes considered include the safety case, safety assessment, accident investigation, and the commonality between the processes and techniques employed in safety and security engineering.

Papers contain extensive industrial experience as well as recent academic research and are presented under the headings: Independent Safety Assessment, Safety and Security, Accident Investigation, Risk and its Tolerability, Achieving and Arguing the Safety of Modular Systems, and Technologies for Dependability.

Practical Elements of Safety contains the invited papers presented at the Twelfth annual Safety-critical Systems Symposium, held at Birmingham, UK in February 2004. The papers included in this volume focus on the themes of the identification and analysis of risk - using the UK railway as an industry example; safety-integrity levels; industrial use of formal methods; as well as expanding on the development, assessment and changing face of current safety issues. All the papers are linked within the broad context of safety-critical systems actvities and offer a practical perspective. Papers contain industrial experience, as well as academic research, and are presented under the headings of: Mature and Practical Formality, Managing Risk in the Railway Industry, Safety Integrity Levels, the Human Side of Risk, Assessment and the Derivation of Evidence, and Safety Argument and the Law.

Current Issues in Safety-Critical Systems contains the invited papers presented at the eleventh annual Safety-critical Systems Symposium, held in February 2003. The safety-critical systems domain is rapidly expanding and its industrial problems are always candidates for academic research. It embraces almost all industry sectors; current issues in one are commonly appropriate to others. The Safety-critical System Symposium provides an annual forum for discussing such issues. The papers contained within this volume cover a broad range of subjects. They represent a great deal of industrial experience as well as some academic research. All the papers are linked by addressing current issues in safety-critical systems: Dependability Requirements Engineering; Human Error Management; Influences on Risk; Safety Cases; Reforming the Law; Safety Management and Safety Standards.

Components of System Safety contains the invited papers presented at the tenth annual Safety-critical Systems Symposium, held in Southampton, February 2002. The papers included in this volume are representative of modern safety thinking, the questions that arise from it, and the investigations that result. They are all aimed at the transfer of technology, experience, and lessons to and within industry, and they offer a broad range of views. Not only do they show what has been done and what could be done, but they also lead the reader to speculate on ways in which safety might be improved.

Aspects of Safety Management contains the invited papers presented at the ninth annual Safety-critical Systems Symposium, held in Bristol, February 2001. For some time, it has been recognised that technical issues are only one side of the safety coin. The other, often dominant feature, is active, informed and committed management. An understanding of risk, emphasis on education and the use of language, attention to learning lessons from both research and other industry sectors, and the development of the appropriate staff competences, are all aspects of safety management. The papers contained within this volume cover a broad range of subjects, but all have the common link of safety management. They present a great deal of industrial experience, as well as some recent academic research.

Lessons in System Safety contains the full set of invited papers presented at the Eighth Annual Safety-critical Systems Symposium, held in Southampton, February 2000. The safety-critical systems domain is rapidly expanding, and its industrial problems are always candidates for academic research. It embraces almost all industry sectors, and lessons learned in one are commonly appropriate to others. The Safety-critical Systems Symposium provides an annual forum for discussing such problems, and the papers in this volume, being from both industrial and academic institutions, all offer lessons in system safety.

Each year the Safety-critical Systems Symposium brings together practitioners and researchers in a quest to inculcate a higher degree of safety engineering into the development and operation of critical software-based systems. On this, the Symposium's seventh occasion, it explores recent work and experience which lead us further 'towards system safety'. This book of the Proceedings covers the entire event. The first paper is the course text of a tutorial run on the first day of the Symposium, included here to provide readers with a coverage of the entire event. The next fourteen papers were presented, on the second and third days, in six sessions: Safety Cases, Systems Engineering, Safety Analysis and Safety Integrity, Tools for Software Safety, Solving Safety Problems, and Qllestions and Competences. Eight of the fourteen papers were authored in industry, four in universities, and two in other research establishments. Four of them report on work outside the UK: in France, Germany, Norway and Brazil. There are three papers on safety cases, each taking a different perspective. Skogstad from Norway and Boyce and Hamilton of GEC-Marconi both report on experience in the field, the former in attempting to apply European norms to project documentation and the latter in attempting to build up a retrospective safety case. The third paper, by Goodman, takes a more philosophical stance, examining the lack of useful measurement in safety assurance.

This book contains the Proceedings of the 6th Safety-critical Systems Sympo sium, the theme of which is Industrial Perspectives. In accordance with the theme, all of the chapters have been contributed by authors having an industrial af filiation. The first two chapters reflect half-day tutorials - Managing a Safety-critical System Development Project and Principles of Safety Management - held on the first day of the event, and the following 15 are contributed by the presenters of papers on the next two days. Following the tutorials, the chapters fa l into five sub-themes - the session titles at the Symposium. In the first of these, on 'Software Development Tech nology', Trevor Cockram and others report on the industrial application of a requirements traceability model, Paul Bennett on configuration management in safety-critical systems, and Brian Wichmann on Ada. The next 5 chapters are on 'Safety Management'. In the safety domain, the fundamental business of management is increasingly being addressed with respect not merely to getting things done, but also to controlling the processes by which they are done, the risks involved, and the need not only to achieve safety but to demonstrate that it has been achieved. In this context, Gustaf Myhrman reveals recent developments for safer systems in the Swedish De fence, and Shoky Visram reports on the management of safety within a large and complex Air Traffic Control project."

Dependability has always been an vital attribute of operational systems, regardless of whether they are highly-specialised (like electricity generating plants) or more general-purpose (like domestic appliances). This volume provides a highly-readable overview of the topic, concentrating on dependability as a life-cycle management issue rather than as a technical subject. Specifically avoiding technical language and complex mathematics, it is designed to be accessible to readers at all levels. It will be of particular interest to project managers and software engineers in industries where dependability is of particular importance, such as aerospace, process control, and mining. It will also provide useful reading material for students taking courses with modules in dependability. Felix Redmill and Chris Dale have both worked in industry for over 15 years, and now run successful consultancy businesses.

The contributions to this book are the invited papers presented at the fifth annual Safety-critical Systems Symposium. They cover a broad spectrum of issues affecting safety, from a philosophical appraisal to technology transfer, from requirements analysis to assessment, from formal methods to artificial intelligence and psychological aspects. They touch on a number of industry sectors, but are restricted to none, for the essence of the event is the transfer of lessons and technologies between sectors. All address practical issues and of fer useful information and advice. Contributions from industrial authors provide evidence of both safety con sciousness and safety professionalism in industry. Smith's on safety analysis in air traffic control and Rivett's on assessment in the automotive industry are informative on current practice; Frith's thoughtful paper on artificial intelli gence in safety-critical systems reflects an understanding of questions which need to be resolved; Tomlinson's, Alvery's and Canning's papers report on collaborative projects, the first on results which emphasise the importance of human factors in system development, the second on the development and trial of a comprehensive tool set, and the third on experience in achieving tech nology transfer - something which is crucial to increasing safety."

Safety-critical systems, in the sense of software-based systems used in safety critical applications, are 'high-tech'. They are products of modern technology. Their effective, efficient and safe functioning depends not only on the devel opment of the right technologies but also on the right use of them. The safety of a system may be compromised not only by faults in the system but also by the use in the first place of an unreliable, unsafe, or unproved technology in its development. The key to the development and use of both technologies and systems is the human being. Until recently, the importance of human involvement, other than at the direct operational level, was hardly admitted. But now the unreliability of humans is recognised, as is the potential for latent faults to be introduced into systems at any point in their life cycles, by all who are in volved with them, including designers and strategic decision makers."

Each year there are improvements in safety-critical system technology. These arise both from developments in the contributing technologies, such as safety engineering, software engineering, human factors and risk assessment, and from the adoption or adaptation of appropriate techniques from other domains, such as security. For these improvements to be of real benefit, they need to be applied during the appropriate stage in the life cycle of the system, whether it be development, assessment, or operation. For this to occur, they must be communicated and explained. Each year the Safety-critical Systems Symposium offers a distinguished forum for the presentation of papers on such developments, and also for papers from industry on the lessons learned from the use of technologies and methods. The results of many collaborative research projects, with components from both industry and academia, are reported in a universally understandable form. In 1995 the Symposium was held in Brighton, a venue calculated to stimulate not just the presenters of papers, but all the delegates. Yet, this book of Proceedings is intended not only for the delegates but also for readers not able to attend the event itself. We welcome both categories of reader. Delegates have the benefit of attending the presentations and the opportunity to participate in the discussions; those who take up this book after the event can peruse it attheir leisure and, perhaps, on account of it will resolve to attend subsequent symposia.

The programme for the Second Safety-critical Systems Symposium was planned to examine the various aspects of technology currently employed in the design of safety-critical systems, as well as to emphasise the importance of safety and risk management in their design and operation. assessment There is an even balance of contributions from academia and industry. Thus, industry is given the opportunity to express its views of the safety-critical domain and at the same time offered a glimpse of the technologies which are currently under development and which, if successful, will be available in the medium-term future. In the field of technology, a subject whose importance is increasingly being recognised is human factors, and there are papers on this from the University of Hertfordshire and Rolls-Royce. Increasingly, PLCs are being employed in safety-critical applications, and this domain is represented by contributions from Nuclear Electric and August Computers. Then there are papers on maintainability, Ada, reverse engineering, social issues, formal methods, and medical systems, all in the context of safety. And, of course, it is not possible to keep the 'new' technologies out of the safety-critical domain: there are papers on neural networks from the University of Exeter and knowledge-based systems from ERA Technology.

0 e This is the proceedings of the first annual symposium of the Safety-critical Systems Club (The Watershed Media Centre, Bristol, 9-11 February 1993), which provided a forum for exploring and discussing ways of achieving safety in computer systems to be used in safety-critical industrial applications. The book is divided into three parts, which correspond with the themes of the three days of the symposium. The first - "Experience from Around Europe" - brings together information on developments in safety-critical systems outside the UK. The second - "Current" "Research" - consists of papers on large projects within the UK, which involve collaboration between academia and industry, providing techniques and methods to enhance safety. The final part - "Achieving and Evaluating Safety" - explores how methods already in use in other domains may be applied to safety, and examines the relationships between safety and other attributes such as quality and security. The papers identify the current problems and issues of interest in the field of safety-critical software-based systems, and provide valuable up-to-date material for those in both academia and industry. The academic will benefit from information about current research complimentary to his own, and the industrialist will learn of the technologies which will soon be available and where to find them.