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