Suppose there are two signals: A dog barking (\(d\)) and a cat howling (\(c\)). Furthermore, suppose there are three states \(w_1\), \(w_2\) in which the dog barks and \(w_3\) in which the cat howls. The event that there is no intruder is \(E=\{w_1\}\) (the lack of the two signals indicates that there was no intruder[18]).  The following possibility structure (where there is an arrow from state \(w\) to state \(v\) provided \(v\in P(w)\)) describes the inspector’s epistemic state: