  We consider two simple variants of a framework for reasoning about knowledge
amongst communicating groups of players. Our goal is to clarify the resulting
epistemic issues. In particular, we investigate what is the impact of common
knowledge of the underlying hypergraph connecting the players, and under what
conditions common knowledge distributes over disjunction. We also obtain two
versions of the classic result that common knowledge cannot be achieved in the
absence of a simultaneous event (here a message sent to the whole group).
