On the expressive power of inquisitive epistemic logic
Abstract
Inquisitive modal logic, InqML, in its epistemic incarnation, extends standard epistemic logic to capture not just the information that agents have, but also the questions that they are interested in. We use the natural notion of bisimulation equivalence in the setting of InqML, as introduced in [Ciardelli/Otto: JSL 2021], to characterise the expressiveness of InqML as the bisimulation invariant fragment of first-order logic over natural classes of two-sorted first-order structures that arise as relational encodings of inquisitive epistemic (S5-like) models. The non-elementary nature of these classes crucially requires non-classical model-theoretic methods for the analysis of first-order expressiveness, irrespective of whether we aim for characterisations in the sense of classical or of finite model theory.
Keywords
Cite
@article{arxiv.2312.14573,
title = {On the expressive power of inquisitive epistemic logic},
author = {Ivano Ciardelli and Martin Otto},
journal= {arXiv preprint arXiv:2312.14573},
year = {2025}
}
Comments
this is a second companion paper to arXiv:1803.03483 (after Journal of Symbolic Logic 86(1), pp.77-109, 2021. doi:10.1017/jsl.2020.77). This revised version corrects a technical mistake in the main part of previous versions and attempts to improve presentation, largely in response to anonymous referee reports which we gratefully received; correction of typos in previous version