11.1 Introduction


• This chapter will assume that a system or component is functional, or not. In practice systems fail slowly, but we will consider failure to be when they cease being functional.


• No system is perfect and will fail eventually, being able to predict this allows us to determine the useable life.


• Dependability is a combination of,

- reliability - the probability that a system operates through a given operation specification.

- availability - the probability that the system will be available at any instant required.


• Typical failures follow the following curve.