11. The computer program product of claim 10 , wherein the determining further comprises generating a classification tree for a subject, the classification tree specifying subset relationships among the set of subscription queries via hierarchical levels and nodes; wherein each node in a left branch of a parent node at a specified level in the classification tree is a subset of the parent node; and wherein further, subscription queries that are not classified as either of a subset and a superset of the parent node are placed in an empty leaf node by traversing the classification tree for a first available empty leaf node.
11. The computer program product of claim 10 , wherein the determining further comprises generating a classification tree for a subject, the classification tree specifying subset relationships among the set of subscription queries via hierarchical levels and nodes; wherein each node in a left branch of a parent node at a specified level in the classification tree is a subset of the parent node; and wherein further, subscription queries that are not classified as either of a subset and a superset of the parent node are placed in an empty leaf node by traversing the classification tree for a first available empty leaf node. 13. The computer program product of claim 11 , further comprising instructions for implementing: processing the left branch of the one or more selected nodes, comprising: comparing contents of the at least one notification message to each of the subscription queries in each of the nodes of the left branch; and transmitting the at least one notification message to those subscription client systems associated with any of the nodes of the left branch for which a match is found in response to the comparing.