Just moved to Drools 5.1, using a Guvnor package as the base for a Knowledge Base with incremental updating enabled. Our resource is a Guvnor PKG. We encounter the following error when a snapshot is made: [2010:08:224 16:08:903:debug] KnowledgeAgent: Diffing: [UrlResource path=' http://localhost:1337/drools-guvnor/org.drools.guvnor.Guvnor/package/TEST... '] [2010:08:224 16:08:935:debug] BinaryResourceDiffProducerImpl: Comparing [Rule name=Resource Null-Checker, agendaGroup=MAIN, salience=0, no-loop=false] against [Rule name=Resource Null-Checker, agendaGroup=MAIN, salience=0, no-loop=false] Exception in thread "Thread-30" org.drools.RuntimeDroolsException: java.lang.reflect.InvocationTargetException : [Rule name=Resource Null-Checker, agendaGroup=MAIN, salience=0, no-loop=false] at org.drools.core.util.ReflectiveVisitor.visit(ReflectiveVisitor.java:56) at org.drools.agent.impl.BinaryResourceDiffProducerImpl.diff(BinaryResourceDiffProducerImpl.java:63) at org.drools.agent.impl.KnowledgeAgentImpl.incrementalBuildResources(KnowledgeAgentImpl.java:785) at org.drools.agent.impl.KnowledgeAgentImpl.buildKnowledgeBase(KnowledgeAgentImpl.java:586) at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:185) at org.drools.agent.impl.KnowledgeAgentImpl$ChangeSetNotificationDetector.run(KnowledgeAgentImpl.java:1106) at java.lang.Thread.run(Unknown Source) Caused by: java.lang.reflect.InvocationTargetException 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 org.drools.core.util.ReflectiveVisitor.visit(ReflectiveVisitor.java:47) ... 6 more Caused by: java.lang.RuntimeException: this MVELReturnValueExpression must be compiled for equality at org.drools.base.mvel.MVELReturnValueExpression.equals(MVELReturnValueExpression.java:123) at org.drools.rule.ReturnValueRestriction.equals(ReturnValueRestriction.java:306) at org.drools.rule.ReturnValueConstraint.equals(ReturnValueConstraint.java:121) at java.util.Arrays.equals(Unknown Source) at org.drools.rule.OrConstraint.equals(OrConstraint.java:132) at java.util.AbstractList.equals(Unknown Source) at org.drools.rule.Pattern.equals(Pattern.java:317) at org.drools.rule.GroupElement.equals(GroupElement.java:273) at org.drools.agent.impl.BinaryResourceDiffProducerImpl.compareRules(BinaryResourceDiffProducerImpl.java:258) at org.drools.agent.impl.BinaryResourceDiffProducerImpl.visitRule(BinaryResourceDiffProducerImpl.java:117) ... 11 more The rule in question is quite straight-forward, works on the initial load up and worked in 5.0.1 fine. It is not the rule that was just changed. If I remove that rule, another is just substituted in its place in the error message. What might be causing this? If you need more information, please ask. Stephen -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users