A focused proof system provides a normal form to cut-free proofs in which the application of invertible and non-invertible inference rules are structured. Within linear logic, the focused proof system of Andreoli provides an elegant and comprehensive normal form for cut-free proofs. Within intuitionistic and classical logics, there are various different proof systems in the literature that exhibit focusing behavior. These focused proof systems have been applied to both the proof search and the… CONTINUE READING

Zur intuitionistischen arithmetik und zahlentheorie. Ergebnisse eines Mathematischen Kolloquiums, pages 34–38, 1932. English translation in The Undecidable (M