22. The method of claim 21 , where determining the ranks comprises: increasing the ranks of one or more of the plurality of documents that include the keyword and that are associated with one or more of the plurality of categories that are related to the keyword relative to another one or more of the plurality of documents that either do not include the keyword or are not associated with the one of the plurality of categories that are related the keyword.
21. The method of claim 20 , further comprising: identifying the subset of the plurality of documents mapped to the one of the plurality of categories associated with the keyword.