HOL-Z 2.0: A Proof Environment for Z-Specifications

The design of tools for formal specification languages (SL) can be roughly divided into two categories: special purpose design strives for implementing an SL and its method straight-forwardly in an implementation language. In contrast, embedded designs are based on a logical embedding in theorem prover environments such as Isabelle. Examples for the former are Z/EVES, KIV or FDR, examples for the latter are VHDL, HOL-Unity, HOL-CSP and HOL-Z. The advantage of embedded designs such as HOL-Z (whose underlying conservative embedding into higher-order logic (HOL) has been described in [1]) is its solid logical basis: all symbolic computations on formulas are divided into “logical core theorems” (i.e. derived rules) and special tactical programs controlling their application. Thus, logical consistency of the tool for SL can be reduced to the consistency of the underlying meta-logic and the correctness of the underlying logical engine. The problems with embedded designs are threefold: