[rules-users] New to rules engine - help in defining rules

Hello all, I am looking for a way to define rules for the following problem: class Tree { ... } class Branch { Tree mytree; int branch_length; ... } Let's say I have a fact called Tree and another fact called Branch. Brach identifies which tree it belongs to. Now, I want to write a rule to say that all branches in a tree must be of same length. How do I do this with/without using accumulate or forall? Thanks a lot for any help, J