[Zope] catalog-aware z-classes

Hi, I need to create a number of z-classes to represent objects, and want them to be catalog aware, with each having its own catalog. The example in the Zope book requires the catalog to have the id 'Catalog' or it won't work, as this is the default for ZCatalog-aware objects. But I'll need different ids, as I have more than one catalog. How can I override this default? thanks, Ben Avery