Hi All, As my ZODB data files become larger and larger I am looking at ways to make the structure of my objects more efficient. To simplify my question, suppose I have two different classes and both contain a list of a objects from a third class: class x has the attribute x.elements = [objects of class z] class y has the attribute y.elements = [objects of class z] As far as I understand python the lists x.elements and y.elements contain pointers to the z objects previously defined. What I wanted to know is how ZODB handles that (or maybe I should say: how pickle handles that) when saving to a file. Will the pointers be converted to a copy of the z class objects or will one copy of the z class objects be saved and than the x.elements and y.elements will still be a list of pointers? Thanks for the help, Yair -- Yair Benita Utrecht University The Netherlands