[rules-users] Handling maps in Drools

Hi, I am facing an issue with handling maps in LHS of drools. Appreciate your help with the same.  I am using Drools version 5.1. I have two maps where one is a reference map that contains certifications (key) and scores(value) required and other is map of user's actual certifications and scores. Objective is to find the certifications from users map based on keys in the reference map . Then for these certifications sum the score values and check if they cross the threshold. While trying to do the first step i am facing an issue . My rule looks like this :- rule "Map test" when     $rb : Certifications($reqCertificationKeys : requiredCertifications.keySet)     $user : User($userCertifications : userCertifications)     $arg : String() from $reqCertificationKeys        HashMap ($value : this[$arg] != null) from $userCertifications // Does not work then     System.out.println ("Hash Map" + $arg); end However if i change the above line that has issues with below     HashMap ($value : this["Java"] != null) from $userCertifications // Works Is there a way to replace the key with a variable than with a fixed value ? Is it possible to iterate the second map with the key values that we get from the reference map ? Regards, Manav