Complete Cyclic Proof Systems for Inductive Entailments

TL;DR

This paper introduces cyclic proof systems for inductive entailment problems involving recursive predicates with constraints in specific logical fragments, providing soundness, completeness, and decision procedures.

Contribution

It develops novel cyclic proof systems for inductive entailments with constraints in first-order and separation logic, including soundness, completeness, and complexity analysis.

Findings

Proof systems are sound and complete under certain restrictions.

Decidability and complexity results are established for the logical fragments.

A semi-algorithm for entailment decision procedures is provided.

Abstract

In this paper we develop cyclic proof systems for the problem of inclusion between the least sets of models of mutually recursive predicates, when the ground constraints in the inductive definitions belong to the quantifier-free fragments of (i) First Order Logic with the canonical Herbrand interpretation and (ii) Separation Logic, respectively. Inspired by classical automata-theoretic techniques of proving language inclusion between tree automata, we give a small set of inference rules, that are proved to be sound and complete, under certain semantic restrictions, involving the set of constraints in the inductive system. Moreover, we investigate the decidability and computational complexity of these restrictions for all the logical fragments considered and provide a proof search semi-algorithm that becomes a decision procedure for the entailment problem, for those systems that fulfill the restrictions.