9. The method of claim 7 , further comprising: for each rule set, adding a rule set identifier to the search key to generate a final search key for that rule set; and performing the final search for each rule set using the final search key for that rule set, wherein the final searches are performed using a combined search structure comprising the rule data for all rule sets, the rule data for each rule set being associated in the search structure with the rule set identifier for that rule set.
7. The method of claim 1 , farther comprising performing the final searches using a separate search structure for each rule set, each search structure comprising the rule data for a respective rule set.