I tried using FireAllRules each time i inserted an object instead of FireUntilHalt in another thread. Unfortunately it results in the same error message : Unable to Analyse Expression this != $start && after0.evaluate( $start, this ): [Error: unable to resolve method using strict-mode: com.sample.RawEvent.after0()] [Near : {... this != $start && after0.evaluate( $start, this ....}] ^ : [Rule name='Detect it'] java.lang.IllegalArgumentException: Could not parse knowledge. at com.sample.DroolsTest.readKnowledgeBase(DroolsTest.java:106) at com.sample.DroolsTest.main(DroolsTest.java:54) -- View this message in context: http://drools.46999.n3.nabble.com/before-after-behavior-for-negative-patt... 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