Software Dependability
The purpose of this paper is to provide a brief introduction of Software Dependability and a summary of lessons learned. The components of Software Dependability vary among standards, however there is agreement among the standards that reliability, availability and maintainability are some the main components of dependability. Safety is also a main component is safety systems. Although reliability and safety are similar there is an additional difference, safety can withstand some level of fault tolerance. For the purposes of this discussion Software Dependability includes reliability, availability, maintainability and safety. Software Dependability: Trustworthiness of a computer system such that reliance can be justifiably placed on the service it delivers. Reliability, availability, and maintainability are aspects of dependability. Reliability: The ability of a system or component to perform its required functions under stated conditions for a specified period of time. Availability: The degree to which a system or component is operational and accessible when required for use. Often expressed as a probability. Maintainability: Speed and ease with which a program can be corrected or changed. Safety: a measure of the length of time the software system can be expected to run before failing in such a way as to cause a system hazard. (author)