41. The at least one computer-readable storage medium article of claim 37 , wherein items in the plurality of items are represented as tuples, each tuple comprising values of the attributes of the corresponding item, and wherein receiving the plurality of first-order preferences comprises: receiving a first-order preference for the first item over the second item by receiving an indication of a user preference for a first value of a first attribute of a first tuple representing the first item over a second value of the second attribute of a second tuple representing the second item.
41. The at least one computer-readable storage medium article of claim 37 , wherein items in the plurality of items are represented as tuples, each tuple comprising values of the attributes of the corresponding item, and wherein receiving the plurality of first-order preferences comprises: receiving a first-order preference for the first item over the second item by receiving an indication of a user preference for a first value of a first attribute of a first tuple representing the first item over a second value of the second attribute of a second tuple representing the second item. 42. The at least one computer-readable storage medium article of claim 41 , wherein the first attribute is a same attribute as the second attribute.