this post was submitted on 12 Nov 2024
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Debatable. Saying things in a prose specification doesn't magically make them happen. Tests and reference models can though.
I also don't really agree with the SIL requirements that languages need to have rigorous specifications to be safe. Clearly it's better if they do, but would your rather fly on a rocket controlled by C code or Rust code?
IMO a specification would be really nice to have, but it main purpose is to tick a certification checkbox, which is why the only one that exists was written specifically for that purpose.
The specification does not make anything happen but it enables you to say "the implementation is wrong". Of course, you can say that without a spec as well but what does "wrong" mean then? It just means you personally disagree with its behavior. When "wrong" means "inconsistent with the spec" everybody involved can work with more clarity and fewer assumptions. Wrong assumptions can kill people flying rockets.
A specification is just another form of implementation that suffers from the very same problem you describe too.
Fair enough. In practice, we resolve it recursively with a higher level specs and at some point it is just "someone wants that". In commercial software development (where SIL is used) that is a customer who pays for it or some executive.