I'm using code such as KnowledgeRuntime knowledgeRuntime; for( KnowledgePackage knowledgePackage: knowledgeRuntime.getKnowledgeBase().getKnowledgePackages() ){ for( Rule rule: knowledgePackage.getRules() ){ } } to obtain rules, intending to construct a Set<Rule>. This, however, breaks since repeated executions of knowledgePackage.getRules() appear to return different objects and - this is the evil thing - org.drools.definitions.rule.impl.RuleImpl does not implement hashCode() and equals(); hence Set<Rules>( rule ).contains( rule ) fails for actually identical rules. I consider this a bug in Drools (5.1). org.drools.definitions.rule.impl.RuleImpl could easily retain a reference to the org.drools.rule.Rule object from which it is built and delegate hashCode/equals to that. -W