The invention provides a method for conducting an auction of a plurality of heterogeneous items. The method comprises making, by offering parties, offers to potential accepting parties for the heterogeneous items. The making begins at a specified time with at least some of the potential accepting parties and at least some of the offering parties represented by software-based agents hosted on terminals connected via a communication network. Any acceptance by any accepting party of any offer from any offering party is binding on the offering party immediately, but is not binding on the accepting party until the auction closes. The method also comprises accepting, by an accepting party, a first offer from a first offering party for the heterogeneous item only if the first offer provides a surplus of at least a minimum surplus amount for the heterogeneous item.