Probabilistic techniques for software verification

The various techniques for verification of proper software behaviour can be separated into probabilistic and deterministic ones. Deterministic techniques mainly qualify for small programs with very high reliability requirements. The probabilistic ones qualify for large programs in the first place. They are mostly based on operating experience and on black box testing; the aspects of software behaviour are dominating in contrast to the questions of its correctness. The outcome of the related investigations is typically a reliability figure and a related level of confidence. This contribution gives some formulae that may be used as rules of thumb. In any particular licensing process, however, things most likely will get so complex that more detailed techniques such as two stage sampling may become important. In these cases it is advisable to engage specialists about probabilistic, because the mathematical complexity of the problem may exceed the scope needed in ''normal'' engineering. (author). 9 refs, 3 figs, 2 tabs