[Zope-dev] ZCatalog and Unique IDs

Hi, I hope this is a stupid question but why does ZCatalog use the URL of an object to uniquely identify it? Why not just use a reference to the object? Persistent object identifiers must exist for the ZODB so why not use them instead? cheers, Chris PS: This would solve all the problems with ZCatalogs and virtually hosted sites... I think the traversal interface is needed for other reasons but it should remove ZCatalog from the list of things that need it... not that I've just been bitten by this or anything ;-)