  We investigate the properties of Inclusion Logic, that is, First Order Logic
with Team Semantics extended with inclusion dependencies. We prove that
Inclusion Logic is equivalent to Greatest Fixed Point Logic, and we prove that
all union-closed first-order definable properties of relations are definable in
it. We also provide an Ehrenfeucht-Fra\"iss\'e game for Inclusion Logic, and
give an example illustrating its use.
