Definitions

Some of these definitions are particular to software engineering, especially the contradictory definitions of fault in computer science and electrical engineering (see below).

  • An error is a design flaw, or deviation from the intended state
  • A failure has occured if the system hasnt performed in some subset of the specified environmental conditions
  • In Computer Science, a fault is produced by an error which in turn produces a failure. Whereas in electrical engineering an error produces a failure which produces a fault.
  • Reliability is measure as the "mean time to failure"
  • An accident is an unintended event that results in a specific level of loss
  • A hazard is a set of conditions on the system, if occur with certain environmental conditions (ie a failure), will lead to an accident.
  • The risk is the probability of a hazard and its severity combined with the exposure (ie how likely the hazard is to cause an accident)
  • Safety relates to freedom from accidents