Information set

(in the theory of games)

The set of all possible situations (positions, states) of a game known to a player at a given moment of time. This set comprises the actual situation. The information set characterizes the knowledge of a player on the preceding situations and choices of his own (memory) and of other players (information). Being in an information set, a player needs to take a decision (to choose an alternative of the information set, i.e. to choose one alternative for all positions in the information set at once), which is realized as an alternative of the position only in an actually-played game.

References

[a1]	J. von Neumann, O. Morgenstern, "Theory of games and economic behavior" , Princeton Univ. Press (1953)
[a2]	A. Rapoport, "$N$-person game theory: Concepts and applications" , Univ. Michigan Press (1970) pp. 92; 97–100
[a3]	J. Szép, F. Forgó, "Introduction to the theory of games" , Reidel (1985) pp. 171; 199