About the actual need and solutions for a formal specification

[ericjenn]

What do we actually need in terms of specification level, specification formalism?
Do we really need a formal specification language (Coq, WhyMl, PVS, Z, etc.) or can we live with something lighter?

[jeansouyris]

If no formal language is used, the "lighter" format shall be sufficiently accurate, consistent and non-ambigous to enable one to derive a specification in a formal language from it.