Attributes
Reliability
Reliability is the probability R(t) that the system will continue functioning at the end of the process.
The time t is measured in continuous working hours between diagnostics. The constant failure rate λ is measured in failures/hour. The useful life of a system component is the constant region (on a logarithmic scale) of the curve between the component's age and its failure rate. The region of the graph before equilibrium is the burn-in phase, and the region where the failure rate starts to increase is the end-of-life phase. Thus, we have R(t) = exp(-λt).
Availability
Dependability
Continuity of service delivery.
It is a measure (probability) of the success with which the system conforms to the definitive specification of its behavior.
Safety
Safety is the absence of conditions that can cause damage and the propagation of catastrophic damage in production.
However, as this definition can classify virtually any process as unsafe, we often consider the term mishap.
Despite its similarity to the definition of Dependability, there is a crucial difference in emphasis: Dependability is the measure of success with which the system conforms to the specification of its behavior, typically in terms of probability, while Safety is the improbability of conditions leading to a mishap occurring, regardless of whether the intended function is performed.
Integrity
Integrity is the absence of conditions that can lead to inappropriate alterations of data in production.