19. The system of claim 18 wherein said program instructions cause the processor to weight each co-occurrence value based upon a probability of occurrence of the corresponding stemmed word within the corpus.
19. The system of claim 18 wherein said program instructions cause the processor to weight each co-occurrence value based upon a probability of occurrence of the corresponding stemmed word within the corpus. 20. The system of claim 19 wherein said program instructions cause the processor to compute the weighting value (w) from the probability of occurrence (p) according to the formula: w=log 2 (p −1 ).