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arXiv · 1804.06689

Duality between unprovability and provability in forward proof-search for Intuitionistic Propositional Logic

Camillo Fiorentini·Mauro Ferrari
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Abstract

The inverse method is a saturation based theorem proving technique; it relies on a forward proof-search strategy and can be applied to cut-free calculi enjoying the subformula property. Here we apply this method to derive the unprovability of a goal formula G in Intuitionistic Propositional Logic. To this aim we design a forward calculus FRJ(G) for Intuitionistic unprovability which is prone to constructively ascertain the unprovability of a formula G by providing a concise countermodel for it; in particular we prove that the generated countermodels have minimal height. Moreover, we clarify the role of the saturated database obtained as result of a failed proof-search in FRJ(G) by showing how to extract from such a database a derivation witnessing the Intuitionistic validity of the goal.

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BibTeXRIS

Camillo Fiorentini, Mauro Ferrari. 2018-04-18. Duality between unprovability and provability in forward proof-search for Intuitionistic Propositional Logic. https://doi.org/10.1145/3372299

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