LNCS 2788 Using IEC 61508 to Guide the Investigation of Computer Related Incidents and Accidents 1st Edition by Chris Johnson ISBN 3540398783 9783540398783

Relatively few investigation techniques have been specifically developed to identify the causal factors that contribute to mishaps involving safety-critical computer systems. The following pages, therefore, presents two complementary investigation techniques that are intended to support the analysis of Electrical, Electronic or Programmable, Electronic Systems (E/E/PES)-related mishaps. One is intended to provide a low-cost and lightweight approach that is appropriate for low consequence events. It is based around a flowchart that prompts investigators to identify potential causal factors through a series of questions about the events leading to a failure and the context in which they occurred. The second approach is more complex. It involves additional documentation and analysis. It is, therefore, more appropriate for incidents that have greater potential consequences or a higher likelihood of recurrence. This approach uses Events and Causal Factors (ECF) modelling promoted by the US Department of Energy (1992). Both approaches provide means of mapping causal factors back to the lifecycle phases and common requirements described in the IEC 61508 standard. This provides an important bridge from the products of mishap analysis to the design and operation of future systems. The UK Health and Safety Executive sponsored this work as part of an initiative to develop analysis techniques for E/E/PES related incidents. The events leading to an explosion and fires in a fractional distillation unit are used to illustrate the application of our techniques. Our techniques are likely to identify incidents that cannot easily be attributed to lifecycle phases or common requirements in IEC 61508. The link between constructive design standards and analytical investigation techniques can, therefore, yield insights into the limitations of these standards. An implicit motivation in our work is to provide the feedback mechanisms that are necessary to improve the application of standards, such as IEC 61508 and DO-178B.