From Herbrand schemes to functional interpretation

Abstract

Herbrand schemes are a method to extract Herband disjunctions directly from sequent calculus proofs, without appealing to cut elimination, using a formal grammar known as a higher-order recursion scheme. In this note, we show that the core ideas of Herbrand schemes can be reformulated as a functional interpretation of classical sequent calculus, similar to the functional interpretation of classical logic due to Gerhardy and Kohlenbach. We argue that this provides a natural computational interpretation of classical sequent calculus, in the same spirit as the game-theoretic approach due to Alcolei et al. that has previously been used to analyze Herbrand's theorem in terms of concurrency.