On semantics of first-order justification logic with binding modalities
Tatiana Yavorskaya, Elena Popova
TL;DR
This paper develops the first-order logic of proofs with binding modalities (FOLP^Box) and provides a Kripke-style semantics using variable valuations via Fitting models. It formalizes axiom systems (FOLP^Box_0 and CS extensions), proves internalization and substitution properties, and then establishes soundness. The core achievement is strong completeness, proven via a canonical Fitting model built from maximal ∃-complete sets and a Truth Lemma that connects syntax to semantics. Overall, the work furnishes a rigorous semantic foundation for first-order justification logics with binding modalities and ties them to canonical modal frameworks.
Abstract
We introduce the first order logic of proofs $FOLP^\Box$ in the joint language combining justification terms and binding modalities. The main issue is Kripke--style semantics for this logic. We describe models for $FOLP^\Box$ in terms of valuations of individual variables instead of introducing constants to the language. This approach requires a new format of the evidence function. This allows us to assign semantic meaning to formulas that contain free variables. The main results are soundness and completeness of $FOLP^\Box$ with respect to the described semantics.
