26. The computer-readable medium of claim 25 , wherein computing a score for the second term comprises: computing respective changes in co-occurrence frequency between corresponding elements of the first vector and the second vector; generating an order of co-occurring terms according to the corresponding computed changes in co-occurrence frequency; and computing a measure of importance of a top number of co-occurring terms in the order.
26. The computer-readable medium of claim 25 , wherein computing a score for the second term comprises: computing respective changes in co-occurrence frequency between corresponding elements of the first vector and the second vector; generating an order of co-occurring terms according to the corresponding computed changes in co-occurrence frequency; and computing a measure of importance of a top number of co-occurring terms in the order. 31. The computer-readable medium of claim 26 , wherein the measure of importance of a term is an inverse document frequency of the term.