http://en.wikipedia.org/wiki/N-version_programming http://en.wikipedia.org/wiki/N-version_programming It's used in Airbus planes, for instance. Of course, it's

http://en.wikipedia.org/wiki/N-version_programming http://en.wikipedia.org/wiki/N-version_programming It's used in Airbus planes, for instance. Of course, it's useless if the specification is wrong, and the assumption that the differing versions will fail in different ways seems to not hold water.