A model of a game is a structure that represents the informational context of a given play of the game. The states, or possible worlds, in a game model describe a possible play of the game and the specific information that influenced the players’ choices (which may be different at each state). This includes each player’s “knowledge” of her own choice and opinions about the choices and “beliefs” of her opponents. A key challenge when constructing a model of a game is how to represent the different informational attitudes of the players. Researchers interested in the foundation of decision theory, epistemic and doxastic logic and, more recently, formal epistemology have developed many different formal models that can describe the many varieties of informational attitudes important for assessing the choice of a rational agent in a decision- or game-theoretic situation.