In a method of determining an optimal allocation in a combinatorial auction, a plurality of bids is received. Each bid includes a plurality of sub bids. Each sub bid includes either one good and a price associated with the good or a logical operator logically connecting at least two child sub bids and a price associated with the logical operator. For each sub bid, the price associated with the good or the logical operator is either an explicit price that is included with the sub bid or is assigned a value of zero when the sub bid does not include an explicit price. An objective is defined for the plurality of bids. For each bid, a plurality of mathematical relationships collectively representing the bid without logical operators is defined. The received bids are processed to achieve the objective subject to the mathematical relationships.