The disclosed implementations provide a method of searching for a known item. The method includes receiving a lookup request for the known item. The lookup request includes information identifying estimated values for a plurality of attributes of the known item. In accordance with the received lookup request, two or more estimated attribute-value pairs for the known item are estimated. In accordance with the received lookup request, a plurality of queries corresponding to the estimated attribute-value pairs are formulated in accordance with a plurality of predefined query types, each query having a corresponding position in a query type hierarchy. One or more candidate items are identified by executing one or more of the plurality of queries in accordance with the query type hierarchy. At least one of the candidate items is returned in response to the lookup request for the known item.