Mechanically supporting case analysis for verification of distributed systems

The OTS/CafeOBJ method can be used to formally model, specify and verify distributed systems such as security protocols and railroad systems. A distributed system is modeled as an OTS, a kind of transition system, and the OTS is specified and verified with CafeOBJ, an algebraic specification language. Case analysis (or case splitting) is one of the most intellectual pieces of work in verification. Case analysis should be done entirely by hand in the OTS/CafeOBJ method, which is errorprone. It is indispensable to cover all cases and find necessary lemmas for some sub-cases where desired results are not obtained in case analysis. We propose two methods of mechanically supporting case analysis, which concern these two issues. A case study that the proposed methods are effectively applied to a railroad signaling system is also reported.