13. The computer program product of claim 11 , wherein the frequency analysis comprises: for each term on the list, counting its occurrences in the document data to obtain a frequency of the term, and calculating a frequency score for the term based on its frequency.
20. The computer program product of claim 13 , wherein the process further comprises: calculating a co-occurrence score for each selected term; and multiplying the frequency score and the co-occurrence score of the selected term to obtain the score of the selected term.