Re: [rules-users] Does Session effeciently filter unused facts, or...

In current Drools versions, you will need to use some "internal APIs" for that, but we can probably add a higher level method call for the next version. The LHS of a rule is a tree of RuleConditionElements. What you need to do is navigate the tree recursively using the getNestedElements() method and looking for Patterns. In pseudo algorithm: *************** Package pkg = ...; // obtain a package from the package builder or from the rulebase Set<Class<?>> usedClasses = new HashSet<Class<?>>(); for( Rule rule : pkg.getRules() ) { RuleConditionElement lhs = rule.getLhs(); collectUsedClasses( usedClasses, lhs ); } ************** public void collectUsedClasses( Set<Class<?>> usedClasses, RuleConditionElement rce ) { if( rce instanceof Pattern ) { ObjectType ot = ((Pattern)rce).getObjectType(); if( ot instanceof ClassObjectType ) { usedClasses.add( ((ClassObjectType)ot).getClassType() ); } } for( RuleConditionElement child : rce.getNestedElements() ) { collectUsedClasses( usedClasses, child ); } } ****************** I wrote the above code directly into the e-mail, so there might be some mistakes, but the idea is there... so you can probably figure out, based on that. Edson 2009/11/24 Barry Kaplan <groups1(a)memelet.com&gt; -- Edson Tirelli JBoss Drools Core Development JBoss by Red Hat @ www.jboss.com