1. A method comprising: accessing product category information identifying various products in a particular product category in an inventory of a network database, the product category information further identifying a set of attributes associated with the products in the particular product category; calculating, using one or more processors, an importance value associated with each of the attributes; the importance values indicating an importance of each of the attributes for uniquely identifying the products in the product category, attributes having a greater statistical variation among the products in the product category being associated with a greater importance value, attributes having a smaller statistical variation among the products in the product category being associated with a smaller importance value; ranking the attributes, based on the importance value associated with each of the attributes; transmitting, from a server over a network, instructions to cause a client machine to generate a user interface that is configured to display one or more user interface entry fields; receiving, at the server over the network, a user specification of a product category in connection with a user request to post an item listing and a user specification of one or more values associated with one or more of a subset of the ranked attributes; identifying the subset of the ranked attributes from the network database, based on the receiving of the user specifications, each ranked attribute having at least a predetermined ranking; and mapping the item listing to one of the products in the product category in the inventory of the network database, based on the user specified values.