I am trying to get a project that runs in Drools 3 working on Drools 4. Several of the rules in our DRL file are failing for the same reason, which is described below. I have searched for documentation where someone encountered this error, but have found none, which is why I am writing the list. Here is a sample rule that fails: rule 'X' salience 750 when s : Sensor( source == "Not in File" , TCN matches "CRM[0-9]+MXFS[0-9]+" ) then System.out.println("Rule executed: X " ); s.setSource("X"); System.out.println( "in rule location 2"); update(s); System.out.println( "in rule location 3"); end The rule fails when the "update(s);" statement is executed, with the error that a String cannot be converted to a long (stack trace is below). The Sensor class has several variables. The last getter method called before the failure returns a long. The source variable (which is set in the RHS of the rule) is a String , and the for source is the 2nd to last getter called. Does anyone have an idea why this update statement would fail - why it would be trying to convert a String to a long? Thank you, David Warren Stack trace: org.drools.RuntimeDroolsException: Conversion to long not supported from java.lang.String at org.drools.base.extractors.BaseObjectClassFieldExtractor.getLongValue(Ba seObjectClassFieldExtractor.java:106) at org.drools.base.ClassFieldExtractor.getLongValue(ClassFieldExtractor.jav a:203) at org.drools.rule.VariableRestriction$LongVariableContextEntry.updateFromT uple(VariableRestriction.java:284) at org.drools.common.SingleBetaConstraints.updateFromTuple(SingleBetaConstr aints.java:100) at org.drools.reteoo.JoinNode.assertTuple(JoinNode.java:102) at org.drools.reteoo.CompositeTupleSinkAdapter.createAndPropagateAssertTupl e(CompositeTupleSinkAdapter.java:73) at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode .java:116) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(Compo siteObjectSinkAdapter.java:318) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:140) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(Compo siteObjectSinkAdapter.java:299) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:153) at org.drools.reteoo.Rete.assertObject(Rete.java:175) at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192) at org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java: 71) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.jav a:909) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.jav a:881) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.jav a:67) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.jav a:61) at com.bah.aims.rules.Rule_X_0.consequence(Rule_X_0.java:32) at com.bah.aims.rules.Rule_X_0ConsequenceInvoker.evaluate(Rule_X_0Consequen ceInvoker.java:22) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:550) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:514) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemo ry.java:471) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemo ry.java:433) at com.bah.aims.rules.compiler.SensorPairRulesTest.testNotInFileIqcrm(Senso rPairRulesTest.java:27) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at junit.framework.TestCase.runTest(TestCase.java:154) ...