9126-1 Quality Model: Reliability
2. A set of attributes related to the capability of the software system to maintain its level of performance under stated conditions for a stated period of time.
2.a Maturity, attributes related to the frequency of failure by faults in the software system.
2.b Fault tolerance, attributes related to the ability of the software system to maintain a specified level of performance in cases of software faults or of infringement of its specified interface.