1. A method of classifying a document using a duplicate detector and an inductive classifier, the method comprising: generating, at the duplicate detector, a lexicon of attributes based on attribute information received from the inductive classifier, wherein the duplicate detector is configured to determine whether two or more data items are near duplicates of each other; receiving, at the duplicate detector, a set of documents of known classification; calculating, at the duplicate detector, class signatures based on the set of documents of known classification and the lexicon of attributes; receiving, at the duplicate detector, an unknown document; generating, at the duplicate detector, a query signature based on the unknown document and the lexicon of attributes; comparing, at the duplicate detector, the query signature to the class signatures to determine whether the query signature matches a class signature; when the query signature matches a class signature, indicating the unknown document has a class of the document corresponding to the class signature that matches the query signature; and when the query signature does not match a class signature, providing the unknown document to the inductive classifier.