5. The method of claim 4 , wherein the score satisfies: score = ∑ i = 1 N ⁢ V i · imp ⁡ ( Term i ) , wherein V i is a change in co-occurrence frequency Term i is a term corresponding to the change in co-occurrence frequency, and imp(Term i ) is an importance of Term i .
4. The method of claim 2 , wherein computing a score for the second term comprises: computing a weighted sum of the changes in co-occurrence frequencies for the top number of co-occurring terms in the order, wherein each change in co-occurrence frequency is weighted by the measure of importance of the corresponding co-occurring term.