10. The method of claim 1 wherein the document is an unknown document and the signature is a query signature, the method further comprising comparing the query signature to known signatures generated from a set of known documents to determine whether the unknown document is a duplicate of one of the set of known documents.
10. The method of claim 1 wherein the document is an unknown document and the signature is a query signature, the method further comprising comparing the query signature to known signatures generated from a set of known documents to determine whether the unknown document is a duplicate of one of the set of known documents. 11. The method of claim 10 wherein comparing the query signature to known signatures generated from a set of known documents comprises determining whether a sub-signature in the query signature is the same as a sub-signature in one of the known signatures.