8. A computer-implemented method according to claim 1 wherein generating the respective relevancies of the vocabulary words comprises: counting how many times a respective vocabulary word is used in the N top ranked documents; and counting how many of the N top ranked documents uses the respective vocabulary word.
9. A computer-implemented method according to claim 8 further comprising generating a word/document ratio for each respective vocabulary word based upon the counting, and if the word/document ratio is less than a threshold, then the relevancy of the word is not used when generating the re-ranking of the N top ranked documents.