Solving quantified modal logic problems by translation to classical logics

This article describes an evaluation of Automated Theorem Proving (ATP) systems on problems taken from the Quantified Modal Logics Theorem Proving (QMLTP) library of first-order modal logic problems. Principally, the problems are translated to both typed first-order and higher-order logic (HOL) in the TPTP language using an embedding approach, and solved using first-order resp. HOL ATP systems and model finders. Additionally, the results from native modal logic ATP systems are considered, and compared with the results from the embedding approach. The findings are that the embedding process is reliable and successful when state-of-the-art ATP systems are used as backend reasoners, the first- and higher-order embeddings perform similarly, native modal logic ATP systems have comparable performance to classical systems using the embedding for proving theorems, native modal logic ATP systems are outperformed by the embedding approach for disproving conjectures and the embedding approach can cope with a wider range of modal logics than the native modal systems considered.