 The conditions needed to verify informational signalling in the sense of [\(\mathbf{IC}\)] rely on the existence of law-like constraints such as natural laws, necessary laws such as those of math, or conventions, thanks to which (in part) one situation may serve as carrier of information about another one. Constraints specify the correlations that exist between situations of various types, in the following sense: if two types \(T\) and \(T '\) are subject to the constraint \(T \Rightarrow T '\), then for every situation \(s\) of type \(T\) there is a relevantly connected situation \(s'\) of type \(T '\). In the radar example, the relevant correlation would be captured by the constraint GoingUpward \(\Rightarrow\) GoingNorth, which says that each situation where a radar point moves upward is connected with another situation where a plane is moving to the north. It is the existence of this constraint that allows a particular situation where the dot moves to indicate something about the connected plane situation. 