Itai Ashlagi

This talk consists of two parts:

1. We show that weighted VCG are the only truthful-revealing symmetric position auctions.

2. A mediator is a reliable entity, which plays on behalf of the players who give her the right of play. The mediator is guaranteed to behave in a pre-specified way based on messages received from the agents.

However, a mediator can not enforce behavior; that is, agents can play in the game directly without the mediator's help. A mediator generates a new game for the players, the mediated game. The outcome in the original game of an equilibrium in the mediated game is called a mediated equilibrium. Monderer and Tennenholtz defined a mediator for games with complete information. We extend the theory of mediators to games with incomplete information, and use the new theory to study position auctions, a central topic in practical and theoretical electronic commerce. We provide minimal sets of conditions on position auctions, which are sufficient to guarantee that the VCG outcome function is a mediated equilibrium in these position auctions.

Monday, November 19, 2007 4:00 PM 5130 Upson Hall		Theory Seminar Fall 2007 CS 789
	Itai Ashlagi Technion
	Position Auctions and Mediators
	This talk consists of two parts: 1. We show that weighted VCG are the only truthful-revealing symmetric position auctions. 2. A mediator is a reliable entity, which plays on behalf of the players who give her the right of play. The mediator is guaranteed to behave in a pre-specified way based on messages received from the agents. However, a mediator can not enforce behavior; that is, agents can play in the game directly without the mediator's help. A mediator generates a new game for the players, the mediated game. The outcome in the original game of an equilibrium in the mediated game is called a mediated equilibrium. Monderer and Tennenholtz defined a mediator for games with complete information. We extend the theory of mediators to games with incomplete information, and use the new theory to study position auctions, a central topic in practical and theoretical electronic commerce. We provide minimal sets of conditions on position auctions, which are sufficient to guarantee that the VCG outcome function is a mediated equilibrium in these position auctions.