Dependability terminology: similarities and differences

The terminology of the field of dependable computing is used non-uniformly by many authors and standards. This paper presents a survey of definitions drawn from a variety of sources in an attempt to abstract away from the terminology and focus instead on the fundamental concepts underlying the definitions. Two results are reported: first, a characterisation of `dependability´ as a subjective portmanteau of `entities´ and `attributes´; second, a simple, yet rigorous, model for `errors´, `failures´ and `faults´. The latter model leads to a careful examination of the mechanisms by which undesired situations occur and propagate in complex integrated computer systems. The significance of these results is discussed