Hi all, There should be a really simple solution to the problem I'm facing, but want to make sure if the solutions I'm considering are viable ones. I'm designing a shopping cart product. A complete rewrite of its PHP counterpart, which makes use of MySQL as backend. Basically the PHP version uses the following MySQL tables to categorize products and present them to users accordingly: - a category description table: all categories go into this table - a product description table: all descriptions of purchasable products go into this table - a category-product mapping table: the table tells us which product belongs to which category. It **allows** a product to get associated with **multiple** categories. Well, guess it'll be easy to implement the first two tables as objects in Zope. The problem arises from the fact that we should be able to put a product object into multiple category folderish objects without actually **duplicating** it: if a product goes under the Categories A and B and when we delete the product from its parent Category A, it should be also deleted from the Category B. The same logic should also apply when we modify the object. It's much like creating a reference to an object instead of actually deep-copying it when we copy a product from one category to another. I thought about putting all product objects into a single root category ( self-catalogging and BTreeFolderish ) and make subcategories transparent: /Bookstore - root category /aBook - a product object /Thriller - subcategory ( transparent folderish ) /Romance - subcategory ( transparent folderish ) /Romance/Sheldon - sub-subcategory (transparent folderish, will this nested subcategories work? not sure. ) We can visit the aBook object taking advantage of acquisition: - /Bookstore/aBook - /Bookstore/Thriller/aBook - /Bookstore/Romance/aBook - /Bookstore/Romance/Sheldon/aBook Will this work without any problems? What would be the easiest way to implement this? ( Without relying on RDBMS like MySQL , of course :-) Any hints or comments would be greatly appreciated. Cheers, Wankyu Choi --------------------------------------------------------------- Wankyu Choi CEO/President NeoQuest Communications, Inc. http://www.zoper.net http://www.neoboard.net ---------------------------------------------------------------