The development of critical systems often places undue trust in the software tools used. This is especially true of compilers, which are a weak link between the source code produced and the object code which is executed. Stepney [23] advocates a method for the production of trusted compilers (i.e. those which are guaranteed to produce object code that is a correct refinement of the source code) by developing a proof of a small, but non trivial compiler by hand in the Z specification language. This approach is quick, but the type system of Z is too weak to ensure that partial functions are correctly applied.

Here, we present a re-working of that development using the PVS specification and verification system. We describe the problems involved in translating from the partial set theory of Z to the total, higher order logic of the PVS system and the strengths and weaknesses of this approach.

• fme97.dvi
• fme97.ps