8. The method of claim 1 , wherein counting further comprises: computing, for each of the messages of the corresponding set of previously received messages and the second set in which the term and either (i) one of the at least one primary term or (ii) at least two of the secondary terms appears, a weight based on the number of primary and secondary terms appearing in the message; and incrementing the count for the term by an amount determined by the weight.
9. The method of claim 8 , further comprising increasing the miss score for the term by an amount determined by the weight.