 Given that the points of evaluation in relevance logics were understood originally as impossible situations (since they may be both inconsistent and incomplete), the main conceptual move was to understand channels to be special types of situations. The full proofs may be found in Restall (1994) and Mares (1996), and these demonstrate that the expressive power of Barwise’s system may be captured by the frame semantics of relevance logic. What it is that such “combining” of \(x\) and \(y\) amounts to depends on, of course, which structural rules are operating on the frame in question. As explained in the previous section above, the choice of which rules to include will depend on the properties of the phenomena being modelled. 