A player’s strategy can be thought of as the complete instruction for
which actions to take in a game.
For example, a player can give his or
her strategy to a person that has absolutely no knowledge of the player’s
payoff or preferences and that person should be able to use the instructions
contained in the strategy to choose the actions the player desires.
As a result, each player’s set of feasible strategies must be independent
of the strategies chosen by the other players, i.e., the strategy choice
by one player is not allowed to limit the feasible strategies of another
player. (Otherwise the game is ill defined and any analytical results
obtained from the game are questionable.)