When using "or", only one pattern of the or expression will be bound. So, at runtime, onlty one variable $p1 or $p2 exists, and the other is null so the NPE at runtime. By the way, I can't see you are using a or here, as you test exactly the same things ... ----- Mail original ----- De: "Joana Lopes" <joanpl(a)gmail.com&gt; À: rules-users(a)lists.jboss.org Envoyé: Vendredi 18 Mai 2012 13:14:19 Objet: [rules-users] Exception on at org.drools.reteoo.LeftTuple.get(LeftTuple.java:300) drools 5.0.1 Hi There, I'm new to drools and i'm having a problem with a rule which has an OR: /* Rule 25_OFF -------------------------------------------------------------------------------- */ rule "25_OFF" when $p1:InferenceFactValue( param!=null, param.parameterName == "sonar_8_cm", $v1:param.valueFloat >= 10 ) or $p2:InferenceFactValue( param!=null, param.parameterName == "sonar_8_cm", $v2:param.valueFloat >= 10 ) then InferenceUtils.log( LogLevel.DEBUG, InferenceUtils.DROOLS_RULE, "Global Clock: " + InferenceDateUtils.dateString( globalClock, false ), true, false ); InferenceUtils.log( LogLevel.DEBUG, InferenceUtils.DROOLS_RULE, "\t\tRegra 25_OFF " + "25", true, false ); InferenceFactValue[] params = {$p1, $p2}; RuleFire.addEndAlarm( inferenceAgent, droolsEngine, "AlarmPackage", "25", "25", params, globalClock ); end No errors in knowledge builder What happens is: org.drools.runtime.rule.ConsequenceException: java.lang.NullPointerException at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:943) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:885) at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1086) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:660) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:627) at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:183) at pt.holos.dva.agents.inference.process.DroolsInferenceEngine.fireAllRules(DroolsInferenceEngine.java:644) at pt.holos.dva.agents.inference.process.DroolsInferenceEngine.receiveDataFromBuffer(DroolsInferenceEngine.java:342) at pt.holos.dva.agents.inference.process.BufferedDataReceiver.sendDataToDrools(BufferedDataReceiver.java:454) at pt.holos.dva.agents.inference.process.BufferedDataReceiver.run(BufferedDataReceiver.java:68) Caused by: java.lang.NullPointerException at org.drools.reteoo.LeftTuple.get(LeftTuple.java:300) at AlarmPackage.Rule_25_OFF_0ConsequenceInvoker.evaluate(Rule_25_OFF_0ConsequenceInvoker.java:15) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:934) ... 9 more I've tried to see the source code and the declaration in org.drools.reteoo.LeftTuple.get(LeftTuple.java:300) is null. Can you give me some pointers please? Thank you, Joana P Lopes -- LinkedIn - http://pt.linkedin.com/in/joanpl My Bla Bla Bla: http://joanpl.blogspot.com ....................................................... The intuitive mind is a sacred gift and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift. Albert Einstein. "Doubt is not a pleasant condition, but certainty is absurd." Voltaire _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users