Ability to perform as and when required.
In systems engineering, dependability is a measure of a system’s availability, reliability, maintainability, and in some cases, other characteristics such as durability, safety and security. In real-time computing, dependability is the ability to provide services that can be trusted within a time-period. The service guarantees must hold even when the system is subject to attacks or natural failures.
Dependability is often used as a synonym for reliability. However, dependability has a larger scope in that it includes security, performance efficiency, and continuing support and others in addition to reliability.
The IEC-6050-192 (Standard on Dependability):
— Availability: ability to be in a state to perform as required. SOURCE: IEC 60050-192-01-23
— Reliability: ability to perform as required, without failure, for a given time interval, under given conditions. SOURCE: IEC 60050-192-01-24
— Recoverability: ability to recover from a failure, without corrective maintenance SOURCE: IEC 60050-192-01-25
— Maintainability: ability to be retained in, or restored to a state to perform as required, under given conditions of use and maintenance. SOURCE: IEC 60050-192-01-27
— Maintenance support performance: effectiveness of an organization in respect of maintenance support. SOURCE: IEC 60050-192-01-29
— Durability: ability to perform as required, under given conditions of use and maintenance, until the end of useful life. SOURCE: IEC 60050-192-01-21