It is shown that simple and coalitional strategy-proofness of a voting rule as defi?ned on the full unimodal domain of a convex idempotent interval space (X; I) are equivalent properties if (X; I) satis?es interval anti-exchange, a basic property also shared by a large class of convex geometries...

The ß-effectivity function of a strategic game form G describes the decision power of coalitions under G as contingent on the ability of each coalition to predict the behaviour of the complementary coalition. An e¤ectivity function E is ß-playable if there exists a strategic game form G such...