Time is divided into discrete rounds. In the first round, all agents that want to participate in the auction must make an opening bid. If agents want to participate, but do not want to reveal any information about their limit price, they can bid zero or make an unreasonably high offer. On subsequent rounds, any agent can revise its bid/offer. If it does not choose to revise, its existing bid/offer stands.
Trades take place when bids and offers cross, at the average of the two prices.
(Priest and van Tol, 1998)
The Priest-van Tol Environment
The PvT trading periods are defined slightly differently than the IBM market structure. In the PvT, agents continue trading until either all agents have bought/sold, or until no agent is willing to adjest their bid/offer any further. When one of these conditions occurs, the trading period is over, and all agents are reinitialized with an intention to buy/sell one good. (PvTs are not designed to trade multiple units.)