8. A method comprising: by one or more computing devices, deriving 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; by the one or more computing devices, deriving concept terms by extracting significant terms from search text and inferring relevant terms from said significant terms in accordance with the concept matrix; and by the one or more computing devices, generating a query comprising a search expression having at least one of the derived concept terms.
8. A method comprising: by one or more computing devices, deriving 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; by the one or more computing devices, deriving concept terms by extracting significant terms from search text and inferring relevant terms from said significant terms in accordance with the concept matrix; and by the one or more computing devices, generating a query comprising a search expression having at least one of the derived concept terms. 12. The method as recited in claim 8 wherein said query conforms to a Boolean expression.