 In words, \(\omega '\) is reachable from \(\omega\) if there exists a sequence or “chain” of states from \(\omega\) to \(\omega '\) such that two consecutive states are in the same cell of some agent’s information partition. To illustrate the idea of reachability, let us return to the modified Barbecue Problem in which Cathy, Jennifer and Mark receive no announcement. Their information partitions are all depicted in Figure 2.1d: