1. A system for sorting search results according to a buyer profile during the matching phase of an electronic commerce transaction, comprising: a database containing a buyer profile associated with a buyer, the buyer profile comprising a record of the number of times each of a plurality of sort criteria has appeared in at least some previous events involving the buyer; and a server operable to: receive a plurality of search results communicated from one or more seller databases in response to an under-constrained search query in which exact attribute values are not specified for one or more attributes; access the buyer profile to determine an order of display based on the number of times one or more sort criteria in the buyer profile applicable to the search results have appeared in the previous events involving the buyer; sort the search results according to the determined order of display; and communicate the sorted search results to the buyer.