Hello, Please excuse me if I have double posted - my first did not seem to appear. I am wondering if the following is valid rule syntax. I am getting a stacktrace when the rules fire that points to a ClassCastException on a HashSet I am using v4.0 GA. Thank you, Mark rule StateMatch when $ca:CandidateAssociation(nurseDetails.stateLicensures excludes patientDetails.state ) then retract( $ca ); end public class CandidateAssociation { private PatientDetails patientDetails; private NurseDetails nurseDetails; private int overlapHours; public CandidateAssociation( PatientDetails patientDetails, NurseDetails nurseDetails) { super(); this.patientDetails = patientDetails; this.nurseDetails = nurseDetails; overlapHours = participantDetails.getNumberOverlapHourCnt(nurseDetails); } [...] } public class NurseDetails { private Set stateLicensures = new HashSet(); [...] } public class PatientDetails { private String state; [...] } ------------------------------------------------------ Firing Rules ********** org.drools.RuntimeDroolsException: Exception executing predicate org.drools.base.mvel.MVELPredicateExpression@27d6bfb at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:197) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:121) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:317) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:159) at org.drools.reteoo.Rete.assertObject(Rete.java:175) at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:190) at org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:70) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:772) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:64) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:58) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0.consequence(Rule_InitializeCandidateForEachNurse_0.java:13) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.evaluate(Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.java:25) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:503) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:467) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:403) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:384) at primarynursePOC.PrimaryNursePOC.selectPrimaryNurse(PrimaryNursePOC.java:136) at primarynursePOC.PrimaryNursePOC.main(PrimaryNursePOC.java:91) Caused by: java.lang.ClassCastException: java.util.HashSet at org.drools.base.mvel.MVELPredicateExpression.evaluate(MVELPredicateExpression.java:35) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:191) ... 17 more org.drools.RuntimeDroolsException: Exception executing predicate org.drools.base.mvel.MVELPredicateExpression@27d6bfb at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:197) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:121) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:317) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:159) at org.drools.reteoo.Rete.assertObject(Rete.java:175) at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:190) at org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:70) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:772) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:64) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:58) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0.consequence(Rule_InitializeCandidateForEachNurse_0.java:13) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.evaluate(Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.java:25) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:503) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:467) at org.drools.common.AbstractWorkingMemory.doOtherwise(AbstractWorkingMemory.java:430) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:412) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:384) at primarynursePOC.PrimaryNursePOC.selectPrimaryNurse(PrimaryNursePOC.java:136) at primarynursePOC.PrimaryNursePOC.main(PrimaryNursePOC.java:91) Caused by: java.lang.ClassCastException: java.util.HashSet at org.drools.base.mvel.MVELPredicateExpression.evaluate(MVELPredicateExpression.java:35) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:191) ... 18 more Exception in thread "main" org.drools.spi.ConsequenceException: org.drools.RuntimeDroolsException: Exception executing predicate org.drools.base.mvel.MVELPredicateExpression@27d6bfb at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:507) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:467) at org.drools.common.AbstractWorkingMemory.doOtherwise(AbstractWorkingMemory.java:430) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:412) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:384) at primarynursePOC.PrimaryNursePOC.selectPrimaryNurse(PrimaryNursePOC.java:136) at primarynursePOC.PrimaryNursePOC.main(PrimaryNursePOC.java:91) Caused by: org.drools.RuntimeDroolsException: Exception executing predicate org.drools.base.mvel.MVELPredicateExpression@27d6bfb at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:197) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:121) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:317) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:159) at org.drools.reteoo.Rete.assertObject(Rete.java:175) at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:190) at org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:70) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:772) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:64) at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:58) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0.consequence(Rule_InitializeCandidateForEachNurse_0.java:13) at org.drools.examples.Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.evaluate(Rule_InitializeCandidateForEachNurse_0ConsequenceInvoker.java:25) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:503) ... 6 more Caused by: java.lang.ClassCastException: java.util.HashSet at org.drools.base.mvel.MVELPredicateExpression.evaluate(MVELPredicateExpression.java:35) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:191) ... 18 more