It is well known that plausible semantic completeness and consistency conditions for ordinary classical logic are possible in terms of boolean algebras ([11]), and that something similar is possible for both intuitionistic logic and for modal logics via topological structures ([13]). An analogous problem is thc provision of a suitable semantics for the intcnsional system E of cntailment ([1], [2], [3], [6], [7]). Although the general problem remains unsolved, it has nevertheless been possible to provide solutions for at least certain fragments of E ([4], [5], [8]). These...