Checking Computations of Formal Method Tools - A Secondary Toolchain for ProB

We present the implementation of PYB, a predicateand expression-checker for the B language. The tool is to be used for a secondary tool chain for data validation and data generation, with PROB being used in the primary tool chain. Indeed, PYB is an independent cleanroom-implementation which is used to double-check solutions generated by PROB, an animator and model-checker for B specifications. One of the major goals is to use PROB together with PYB to generate reliable outputs for high-integrity safety critical applications. Although PYB is still work in progress, the ProB/pyB toolchain has already been successfully tested on various industrial B machines and data validation tasks.