30. The computer program product of claim 24 , wherein the quality score is based on at least one resource metric of resources identified in response to the revised query, and the navigation score is based on at least one navigation metric of resources identified in response to the revised query.
24. A computer program product, encoded on a computer readable medium, operable to cause a data processing apparatus to perform operations comprising: selecting a candidate query in a query sequence stored in a query log, the query sequence including an initial query and one or more revised queries and defining an order in which the queries were submitted for a search session; selecting a revised query subsequent to the candidate query in the order; determining a quality score for the revised query; determining a navigation score for the revised query; and determining that the quality score for the revised query is greater than a quality score threshold and that the navigation score for the revised query is greater than a navigation score threshold, and in response: identifying a navigational resource for the revised query; and associating the navigational resource with the candidate query, the association specifying the navigational resource as being relevant to the candidate query in a search operation.