Doubly Strongly First Order Dependencies

TL;DR

This paper characterizes which dependency atoms in Team Semantics do not increase the expressive power of First Order Logic, even when combined with negations, clarifying their limitations and capabilities.

Contribution

It provides a full characterization of dependency atoms that are 'doubly strongly first order,' meaning they do not enhance expressiveness when added to First Order Logic with Team Semantics.

Findings

Identifies dependency atoms that do not increase expressiveness

Characterizes the atoms that are 'doubly strongly first order'

Clarifies the expressive limits of Team Semantics extensions

Abstract

Team Semantics is a generalization of Tarskian Semantics that can be used to add to First Order Logic atoms and connectives expressing dependencies between the possible values of variables. Some of these extensions are more expressive than First Order Logic, while others are reducible to it. In this work, I fully characterize the (relativizable) atoms and families of atoms that do not increase the expressive power of First Order Logic with Team Semantics when they and their negations are added to it, separately or jointly (or, equivalently, when they are added to First Order Logic augmented with a contradictory negation connective applicable only to literals and dependency atoms).