Reliability
Software is reliable if the user can depend on it
- reliability is a statistical property
- the probability that software will operate as expected over a specified period of time
- we expect unreliable software, whereas most engineering products are expected to be reliable
Reliability vs. Correctness
- reliability is relative, while correctness is absolute
- given a “correct” specification, correct software is reliable, but not vice versa
- in practice, correct software may not operate as expected or desired