Hi, This problem is almost the same as the problem in 'advice I'. But now only bigger. Much bigger... Assume this : You've products and per each product you need to store : - Information of product - Information of product for customer - Information of product for producer - Information of product for creator - the way it is processed - Link to every machine it is processed - ... Every product is processed by several machines : - Information of machine - Quality Control information - Link to every product passed through this machine - ... .... Everything has to be stored in such a way that it easy accessable and with different queries. Some informations must be combined on a same page, sometimes viewed seperately. Some information depends on the person viewing it (e.g. Information of product /customer/producer/creator) What is the best? Store it in a relational database? Or into Zope? I could make a ZClass of every item, but resulting in tons of properties per ZClass ... and resulting in 1000zends of ZClasses. Is Zope still manageble?? How to make it automatically as possible? ie. adding ZClasses and in such a way that they are correct placed... Somebody ideas? Thanks, Tom.