"To figure out a hierarchical structure among rules" isn't a very clear definition... Rules (like many other logical entities in some programming environment) are written in compilation units - DRL file, which imposes one "hierarchical structure". Then, they are subordinate to "packages" (much like Java classes), which creates another "hierarchical structure". A rule attribute such as "agenda-group" establishes another structure, completely independent from the aforementioned ones, which is effective at runtime, when rules of one group are firing exclusively. Another notion of "hierarchical structure" is introduced by the rule feature "extends", where you can continue the condition of one rule in several other rules. As for interaction: there are many ways you can create "interaction", but typically it will have to be based on facts inserted by one rule and recognized by other rules. As people might interact without direct communication, just by sticking chits on a notice board... -- View this message in context: http://drools.46999.n3.nabble.com/Structuring-rules-in-Drools-tp4022859p4... Sent from the Drools: User forum mailing list archive at Nabble.com.