  Epistemic Logic Programs (ELPs) extend Answer Set Programming (ASP) with
epistemic negation and have received renewed interest in recent years. This led
to the development of new research and efficient solving systems for ELPs. In
practice, ELPs are often written in a modular way, where each module interacts
with other modules by accepting sets of facts as input, and passing on sets of
facts as output. An interesting question then presents itself: under which
conditions can such a module be replaced by another one without changing the
outcome, for any set of input facts? This problem is known as uniform
equivalence, and has been studied extensively for ASP. For ELPs, however, such
an investigation is, as of yet, missing. In this paper, we therefore propose a
characterization of uniform equivalence that can be directly applied to the
language of state-of-the-art ELP solvers. We also investigate the computational
complexity of deciding uniform equivalence for two ELPs, and show that it is on
the third level of the polynomial hierarchy.
