1. A system for discovering bugs, comprising: an input interface configured to: receive an event log; a processor configured to: parse the event log to build an event symptom database; evaluate a bug definition on the event symptom database to determine whether a bug as defined by the bug definition has occurred, wherein the bug definition includes a set operator with a time constraint and one or more set operands, wherein the set operator comprises an interval algebra operator that operates on event symptoms with a time interval, wherein the time interval comprises one of the following: a time interval of an event or a time interval between two events; provide a list of bug occurrences; and a memory coupled to the processor and configured to provide the processor with instructions.