[rules-users] NullPointerException while inserting Facts

Hi, we are currently trying to integrate DROOLS 5.1 in our project. In our Project we have two different kinds of Facts, called Values and Inputs. We don't have any problems with inserting Input instances but sometimes when we try to insert an instance of the Value class (@see: http://www.pastie.org/private/juv7hh7rxahpluo5agu3q) we get the following NullPointerException: java.lang.NullPointerException at org.drools.reteoo.LeftTuple.get(LeftTuple.java:265) at org.drools.reteoo.LeftTuple.get(LeftTuple.java:300) at org.drools.rule.VariableRestriction$ObjectVariableContextEntry.updateFromTuple(VariableRestriction.java:320) at org.drools.common.SingleBetaConstraints.updateFromTuple(SingleBetaConstraints.java:119) at org.drools.reteoo.NotNode.assertLeftTuple(NotNode.java:98) at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:117) at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:34) at org.drools.reteoo.NotNode.assertLeftTuple(NotNode.java:123) at org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:145) at org.drools.reteoo.CompositeLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:57) at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:142) at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:42) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:147) at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:360) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:344) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:185) at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:146) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1046) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1001) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:788) at org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:216) at de.d3web.we.drools.DroolsAction.addFacts(DroolsAction.java:296) at de.d3web.we.drools.DroolsAction.createKnowledgeSession(DroolsAction.java:268) at de.d3web.we.drools.DroolsAction.execute(DroolsAction.java:67) The weird thing is that we don't get this exception with all instances of the Value class - some of them can be inserted, others not. The objects are created correctly - we've already debugged this. The crash happens somewhere deeper in the drools api. It would be really great if you could give us a hint how we could fix this problem. Thank you in advance. Best regards Sebastian Furth