11. The method of claim 10 , further comprising selecting a plurality of fields of the first document likely to contain tokens with high IDF values and selecting the token from the selected fields with the highest inverse document frequency (IDF) with regard to all tokens in the document corpus.
11. The method of claim 10 , further comprising selecting a plurality of fields of the first document likely to contain tokens with high IDF values and selecting the token from the selected fields with the highest inverse document frequency (IDF) with regard to all tokens in the document corpus. 13. The method of claim 11 , wherein the threshold comprises a predetermined number of tokens.