14. One or more computer-readable non-transitory storage media embodying software that is operable when executed by one or more computing devices to: derive a concept matrix from a plurality of sample documents using singular value decomposition of a term-document matrix, the concept matrix identifying a latent pattern of word usage in the plurality of sample documents around a concept; derive concept terms by extracting significant terms from search text and inferring relevant terms therefrom using the concept matrix; and generate a first query for a first index of a first search engine and a second query for a second index of a second search engine, the first and second queries comprising at least one of the derived concept terms.
14. One or more computer-readable non-transitory storage media embodying software that is operable when executed by one or more computing devices to: derive a concept matrix from a plurality of sample documents using singular value decomposition of a term-document matrix, the concept matrix identifying a latent pattern of word usage in the plurality of sample documents around a concept; derive concept terms by extracting significant terms from search text and inferring relevant terms therefrom using the concept matrix; and generate a first query for a first index of a first search engine and a second query for a second index of a second search engine, the first and second queries comprising at least one of the derived concept terms. 16. The media of claim 14 wherein said search text is selected from the group consisting of: a document, an e-mail, and a Web page.