12. The method according to claim 11 wherein the step of partitioning the set of domain keywords comprises the step of controlling relative numbers of domain keywords partitioned into each domain keyword group.
12. The method according to claim 11 wherein the step of partitioning the set of domain keywords comprises the step of controlling relative numbers of domain keywords partitioned into each domain keyword group. 13. The method according to claim 12 wherein the step of controlling relative numbers of domain keywords comprises substantially equalizing, across all the domain keyword groups, a sum for each domain keyword group of the probability for each domain keyword in the each domain keyword group that a randomly selected document from the database includes the each domain keyword.