1. A computer-implemented method of conducting a combinatorial exchange comprising: (a) electronically storing in a computer storage a plurality of bids of a combinatorial exchange, wherein each bid includes at least one item and an associated bid price; (b) electronically associating exchange description data (EDD) stored in the computer storage with at least one of the following: a subset of the received bids, each bid of the subset of the received bids, and/or the combinatorial exchange itself, wherein the EDD stored in the computer storage comprises a representation of at least one of the following features: a non-price attribute of a bid; a non-price attribute of an item; an item adjustment; a bid adjustment; a cost constraint; a unit constraint; a cost requirement; a unit requirement; a counting constraint; a counting requirement; a homogeneity constraint; a mixture constraint; cost conditional pricing; or unit conditional pricing; (c) a model builder electronically constructing a model of (1) the bids received in step (a) and (2) the EDD electronically associated in step (b) with at least one of the following: the subset of the received bids, each bid of the subset of the received bids, and/or the combinatorial exchange itself; (d) a solver/analyzer electronically processing the model constructed in step (c) to determine for the combinatorial exchange an infeasible allocation, a winning allocation or a feasible allocation of received bids and a value for said allocation; and (e) electronically outputting the allocation and the value determined in step (d).