Social processes and proofs of theorems and programs
Communications of the ACM
How to measure software reliability, and how not to
ICSE '78 Proceedings of the 3rd international conference on Software engineering
Theories of Software Reliability: How Good Are They and How Can They Be Improved?
IEEE Transactions on Software Engineering
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An assumption commonly made in early models of software reliability is that the failure rate of a program is a constant multiple of the number of faults remaining. This implies that all faults have the same effect upon the overall failure rate. The assumption is challenged and an alternative proposed. The suggested model results in earlier fault-fixes having a greater effect than later ones (the worst faults show themselves earlier and so are fixed earlier), and the DFR property between fault-fixes (confidence in programs increases during periods of failure-free operations, as well as at fault-fixes). The model shows a high degree of mathematical tractability, and allows a range of reliability measures to be calculated exactly. Predictions of total execution time to achieve a target reliability, and total number of fault-fixes to target reliability, are obtained. It is suggested that the model might also find applications in those hardware reliability growth situations where design errors are being eliminated.