I believe you will need to add each DRL file into a single RuleBase (Drools 4.x terminology; I think KnowledgeBase in 5.0 but I'm a little rusty).
 
Don't forget rules aren't evaluated when "fireAllRules" is called but as objects are inserted into WorkingMemory, so all rules need to be compiled into a RuleBase before object insertion.


From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Amila Silva
Sent: 02 July 2009 11:07
To: rules-users@lists.jboss.org
Subject: [rules-users] How to call a another drl file from one drl file

hi,
   I have requirement to execute a chain of rules. One rule after another and they are reusable.I need to know how to call another drl file from a drl file. or in a then part of the
   a rule.

thanks
Amila Silva