Inclusion Logic and Fixed Point Logic

Abstract

We investigate the properties of Inclusion Logic, that is, First Order Logic with Team Semantics
\nextended with inclusion dependencies. We prove that Inclusion Logic is equivalent to Greatest
\nFixed Point Logic, and we prove that all union-closed first-order definable properties of relations
\nare definable in it. We also provide an Ehrenfeucht-Fraïssé game for Inclusion Logic, and give an
\nexample illustrating its use.