[rules-users] Is "emptieness" supported in Drools 5 (LHS)

According to MVEL they've added a convenience for checking the "emptiness" of a value (see: http://mvel.codehaus.org/Value+Tests ) In MVEL you'd simply write: myMap == empty This seemed like a MUCH cleaner way to write some of the LHS of the rules, so I thought I'd try it out. Given the following rule: rule "Check Empties - Original" when $grabBag : MyGrabBag(someMap != null) eval ($grabBag.getSomeMap().size() == 0) then end This could be rewritten: rule "Check Empties - Simple" when MyGrabBag(someMap == empty) then end The IDE (Eclipse 3.4.2 w/ Drools plugin) seems to recognize "empty" is a keyword (it makes it bold), but the drools compiler in the IDE reports: BuildError: Unable to create restriction '[VariableRestriction: == empty ]' for field 'someMap' in the rule 'Check Empties - Simple' BuildError: Unable to return Declaration for identifier 'empty' Am I assuming incorrectly that the LHS is fully MVEL compliant?