Procedures, programs and their impact on dependability

The dependability of a system can be enhanced by structuring it so as to limit the flow of errors, so that faults do not result in failures. This concept applies to both the mechanical and the human components of a computer-based system (see Chapter 1 of this volume). The present chapter looks at the impact of rules (programs and procedures) on dependability. More precisely, we look into the interaction that rules permit between humans and machines, highlight the strengths and weaknesses of their collaboration and assess the contribution of this collaboration to dependability. These are issues of importance because they shape the structure of the interactions within the organisation and impact on dependability. For instance, such aspects as stability or survivability of computer-based systems depend on how well rules match the cooperative capabilities of technical and non-technical components, the environment and its (expected or unexpected) events.