Knowledge-based (KB) technology is being applied to complex problem-solving and critical tasks in many application domains. Concerns have naturally arisen as to the dependability of knowledge-based systems (KBS). As with any software, attention to quality and safety must be paid throughout development of a KBS and rigorous verification and validation (V&V) techniques must be employed. Research in V&V of KBS has emerged as a distinct field only in the last decade and is intended to address issues associated with quality and safety aspects of KBS and to credit such applications with the same degree of dependability as conventional applications. In recent years, V&V of KBS has been the topic of annual workshops associated with the main AI conferences, such as AAAI, IJACI and ECAI. Validation and Verification of Knowledge Based Systems contains a collection of papers, dealing with all aspects of KBS V&V, presented at the Fifth European Symposium on Verification and Validation of Knowledge Based Systems and Components (EUROVAV'99 - which was held in Oslo in the summer of 1999, and was sponsored by Det Norske Veritas and the British Computer Society's Specialist Group on Expert Systems (SGES).

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.

his volume of the series Lecture Notes in Medical Informatics contains the T proceedings of the Workshop on System Engineering in Medicine, which was held in Maastricht, The Netherlands, 16-18 March 1989. This workshop was sponsored by the EC under the framework of the Medical and Health Research Programme. The aim of the workshop was to assess whether there was sufficient support in the Medical Informatics community in the EC to establish a concerted action. This proceedings contain papers of the presentations given at the workshop. These presentations were centred around three themes: • Methods and Tools • Applications in the domains of chronic care and critical care • Evaluation of decision support systems The papers were prepared after the workshop and therefore we were able to include the relevant parts of the discussions which were related to the presentations. As a result of the discussions during the workshop, a proposal was prepared for the establishment of a concerted action, specifically addressing the development of guidelines for the evaluation of medical decision aids. This proposal was granted early 1990 under the same Medical and Health Research programme of the EC. Over 40 institutes are participating in this concerted action. It have been the outstanding presentations and the open discussions at the workshop that have been the starting point of this concerted action. The papers in this proceedings formed a starting point for the discussions in the meetings of the concerted action.