Patent ID: 8122087

Claim:
A system for event notification, the system comprising a computer-readable storage medium having stored thereon computer-executable instructions configured to: store, on a computer-readable storage medium, a data structure organizing nodes into a hierarchy, the hierarchy including: a first node assigned to a first subscriber request value that identifies a first event, the first node including a first subscriber identifier associated with a first subscriber who submitted a first request to be notified at an occurrence of the first event identified by the first subscriber request value; and a second node assigned to a second subscriber request value that identifies a second event, the second node including a second subscriber identifier associated with a second subscriber who submitted a second request to be notified at an occurrence of the second event identified by the second subscriber request value; receive, from a third subscriber, a third request to be notified at an occurrence of a combination of events including the first event identified by the first subscriber request value and the second event identified by the second subscriber request value; determine that the first event is less likely than the second event to occur; and in response to determining that the first event is less likely than the second event to occur: add, to the hierarchy, a third node including a third subscriber identifier associated with the third subscriber; assign the third node to the second subscriber request value that identifies the more likely second event; and link the first node to the third node; wherein the first node, which is assigned to the first subscriber request value that identifies the less likely first event, is a parent node of the third node, which is assigned to the second subscriber request value that identifies the more likely second event.