30. The apparatus of claim 17, wherein the term signature generating means comprises: selecting means for selecting a reference term in the search query; term vector generating means for generating a term vector for all terms within the search query except for the selected reference term; and combining means for combining the generated term vectors to form the query signature of the reference term.
17. An apparatus for retrieving relevant documents from a corpus of documents based on a search query, the apparatus comprising: storage means for storing the corpus of documents; input means for inputting the corpus of documents and the search query; a controller for retrieving relevant documents from the corpus of documents, the controller comprising: index term signature generating means for generating an index term signature for each index term in the corpus of documents, the index term signature being based on a hash function of a predetermined number of adjacent terms adjacent to the index term; list generating means for generating a list containing the index terms in the corpus of documents, the list associating an index term with a document identifier and corresponding index term signatures occurring in the document; query signature generating means for generating a query signature for the search query excluding a reference term, the query signature being based on the hash function of the adjacent query terms adjacent to the reference term; and comparing means for comparing the query signature to the index term signatures in the list to identify index term signatures that match the query signature of the reference term, the reference term of the query signature being equivalent to the index term of the list; and output means for outputting a document list indicating the documents that contain the identified index term signatures.