PROVERB { A System Explaining Machine - Found ProofsXiaorong

This paper outlines an implemented system called PROVERB that explains machine-found natural deduction proofs in natural language. Diierent from earlier works, we pursue a reconstructive approach. Based on the observation that natural deduction proofs are at a too low level of abstraction compared with proofs found in mathematical textbooks, we deene rst the concept of so-called assertion level inference rules. Derivations justi-ed by these rules can intuitively be understood as the application of a deenition or a theorem. Then an algorithm is introduced that abstracts machine-found ND proofs using the assertion level inference rules. Abstracted proofs are then verbalized into natural language by a presentation module. The most signiicant feature of the presentation module is that it combines standard hierarchical text planning and techniques that locally organize argumentative texts based on the derivation relation under the guidance of a focus mechanism. The behavior of the system is demonstrated with the help of a concrete example throughout the paper.