Hello everybody, currently I'm facing a problem using sliding windows and accumulate feature in Drools 5.5.0.Final. I'm using two sliding windows (window:length) with different lengths on the same event in the same rule. It seems that the shorter window retracts events which are not fitting in it any more, and accumulate function over the bigger window tries to access the retracted event with a NullPointerException. declare Property @role(event) @timestamp(measuretime) end rule "Buggy rule" when Number(doubleValue > 10) from accumulate(Property(propertyname == "PROPERTY1", val16: propertyvalue) over window:length(2) from entry-point "123" , max(val16)) Number(doubleValue < 50) from accumulate(Property(propertyname == "PROPERTY1", val20: propertyvalue) over window:length(5) from entry-point "123" , max(val20)) then System.out.println("Rule Match"); end entryPoint.insert(new Property("PROPERTY1", 20)); session.fireAllRules(); entryPoint.insert(new Property("PROPERTY1", 20)); session.fireAllRules(); entryPoint.insert(new Property("PROPERTY1", 20)); session.fireAllRules(); entryPoint.insert(new Property("PROPERTY1", 2)); session.fireAllRules(); entryPoint.insert(new Property("PROPERTY1", 2)); session.fireAllRules(); entryPoint.insert(new Property("PROPERTY1", 2)); It happens on the last insert. java.lang.NullPointerException at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:1050) at org.drools.reteoo.AccumulateNode.modifyLeftTuple(AccumulateNode.java:345) at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateModifyChildLeftTuple(SingleLeftTupleSinkAdapter.java:259) at org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode.java:676) at org.drools.reteoo.ReteooWorkingMemory$EvaluateResultConstraints.execute(ReteooWorkingMemory.java:590) at org.drools.common.PropagationContextImpl.evaluateActionQueue(PropagationContextImpl.java:350) at org.drools.rule.SlidingLengthWindow.assertFact(SlidingLengthWindow.java:119) at org.drools.rule.BehaviorManager.assertFact(BehaviorManager.java:94) at org.drools.reteoo.WindowNode.assertObject(WindowNode.java:167) at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:497) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:382) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235) at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:127) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:55) Is it a bug, or am I doing something completely wrong? -- View this message in context: http://drools.46999.n3.nabble.com/NullPointerException-using-2-sliding-wi... Sent from the Drools: User forum mailing list archive at Nabble.com.