life critical software

[Henry Spencer]

In article <1857 at dataio.Data-IO.COM> bright at dataio.Data-IO.COM (Walter Bright) writes:
>A typical approach for software would be to have two parallel systems.
>Each system used a different microprocessor, a different algorithm,
>a different language, and different programmers. The two systems
>had to always agree...

One should remember, also, that independent development is not a guarantee
of different algorithms.  There is a strong tendency for programmers to
produce similar solutions to similar problems.  Keeping multiply-redundant
systems truly independent requires systematic attention to be sure that
the problem is indeed being tackled in different ways.
-- 
Allegedly heard aboard Mir: "A |     Henry Spencer at U of Toronto Zoology
toast to comrade Van Allen!!"  | uunet!attcan!utzoo!henry henry at zoo.toronto.edu