  We propose a many-sorted modal logic for reasoning about knowledge in
multi-agent systems. Our logic introduces a clear distinction between
participating agents and the environment. This allows to express local
properties of agents and global properties of worlds in a uniform way, as well
as to talk about the presence or absence of agents in a world. The logic
subsumes the standard epistemic logic and is a conservative extension of it.
The semantics is given in chromatic hypergraphs, a generalization of chromatic
simplicial complexes, which were recently used to model knowledge in
distributed systems. We show that the logic is sound and complete with respect
to the intended semantics. We also show a further connection of chromatic
hypergraphs with neighborhood frames.
