The Propositional Logic of Team Properties

Abstract

Since its introduction by Hodges and refinement by V\"a\"an\"anen, team semantic constructions have been used to generate expressively enriched logics preserving some desirable properties, such as compactness or decidability. By contrast, these logics fail to be substitutional, limiting any algebraic treatment and rendering schematic uniform proof systems impossible. This shortcoming can be attributed to the flatness principle, commonly adhered to when generating team semantics. Investigating the formation of team semantics from algebraic semantics, and disregarding the flatness principle, we present the Logic of Team Properties (LTP), a substitutional logic in which important propositional team logics are axiomatisable as fragments. Starting from classical propositional logic and Boolean algebras, we give a semantics for LTP by considering the algebras that are powersets of Boolean algebras B, that is, of the form P(B), equipped with internal pointwise and external set-theoretic connectives. Furthermore, we present a well-motivated sound and complete labelled natural deduction system for LTP.