1. A system for bug discovery using event reports, comprising: an interface configured to: receive symptom data extracted from event reports from a user system, wherein the symptom data is stored in a symptom database, and wherein the symptom data comprises one or more symptoms each with a corresponding symptom occurrence time; a processor configured to: determine an existence of one or more bugs of the user system based at least in part on a result of querying the symptom database using a bug definition, wherein the bug definition comprises a logic set operation on the symptom data, wherein the logic set operation comprises one of the following: AND, OR, XOR, MINUS, NOT, NAND, NOR or ADD.
14. A system as in claim 1 , wherein the bug definition comprises two or more symptoms that occur with a time dependency between the two or more symptoms.