Below is the code declare EventX @role( event ) @timestamp( eventDate ) @expires( 2m ) end rule "test rule" no-loop when event : EventX(eventType == 'XYZ', $oId :Id) not ( EventY(eventType == 'ABC', Id == $oId, this after[0s,8s] event)) then //fire the rule. code never reaches here if EventY does not occur at all end Can someone help me in understanding what i am doing wrong. I tried removing the not and inserting EventY and it works fine. The eventDate is also populated for both events. Thanks Arun -- View this message in context: http://drools.46999.n3.nabble.com/when-should-we-the-not-operator-tp32259... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users