1. Introduction -- 1. Collective decisions and power structure -- 2. Social choice -- 3. Games and game forms -- 4. The effectivity functions of a game form -- 5. Effectivity functions and cooperative games -- 6. An overview of the book -- 7. Notes -- 2. The structure of effectivity functions --...

We introduce a description of the power structure which is inherent in a strategic game form using the concept of an interaction sheaf. The latter assigns to each open set of outcomes a set of interaction arrays, specifying the changes that coalitions can make if outcome belongs to this open...