 where \(\approx_a\) is the equivalence accessibility relation of agent \(a\). Here one could refine the planes and radar example above by adding some agents, say the controller and the pilot. By relying only on the controls each agent can see, the controller will not be able to distinguish states that agree on the direction of the plane but differ, say, on the metereological conditions around the plane. Those states will be related by the controller’s relation in the model, but not by the pilot’s relation. In principle, this merge of modal epistemic models and constraint models allows one to study, in a single setting, aspects of both the information-as-range and information-as-correlation points of view. The corresponding logical language for epistemic constraint models is the same as for basic constraint models, expanded with the \(K_i\) modal operators, one per agent. The logic is the fusion of the constraint logic from above and a \(S_5\) logic per each agent \(a\). 