Electronic Bidding Service Using an Item Authority

An electronic bidding service is described which substantially automatically acquires items for buyers in response to bidding information entered by the buyers. To function in this manner, the electronic bidding service makes use of an item authority. The item authority links items specified in different offers to master reference information associated with the items, thereby allowing the electronic bidding service to identify groups of offers which are selling the same or related item. In one case, a buyer can instruct the electronic bidding service to obtain a desired item from a specific offer. If this bid is unsuccessful, the electronic bidding service can extend the bidding procedure to one or more other offers that feature the same or related item. This extension is based on the master reference information.