Basic concepts and taxonomy of dependable and secure computing

This paper gives the main definitions relating to dependability, a generic concept including a special case of such attributes as reliability, availability, safety, integrity, maintainability, etc. Security brings in concerns for confidentiality, in addition to availability and integrity. Basic definitions are given first. They are then commented upon, and supplemented by additional definitions, which address the threats to dependability and security (faults, errors, failures), their attributes, and the means for their achievement (fault prevention, fault tolerance, fault removal, fault forecasting). The aim is to explicate a set of general concepts, of relevance across a wide range of situations and, therefore, helping communication and cooperation among a number of scientific and technical communities, including ones that are concentrating on particular types of system, of system failures, or of causes of system failures.

1 Introduction

This paper aims to give precise definitions characterizing the various concepts that come into play when addressing the dependability and security of computing and communication systems. Clarifying these concepts is surprisingly difficult when we discuss systems in which there are uncertainties about system boundaries. Furthermore, the very complexity of systems (and their specification) is often a major problem, the determination of possible causes or consequences of failure can be a very subtle process, and there are (fallible) provisions for preventing faults from causing failures.