-----Original Message----- From: Dave Parker [mailto:dparker@globalcrossing.com]

Yeah, I presumed the "must be installed" issue ;) I'm wondering about the underlying mechanism: when you create an instance of a product, how does it relate to the product itself?

You do not create instances of products, you create instances of classes. A Product can contain multiple classes. An instances cannot be unpickled without its class, so if you remove a class without removing instances of that class the instances will show up as broken (but Zope can handle that, you just can't used the broken objects). Note that ZClasses are identical to python classes. In fact, they *are* python classes. To find out more about that, read any good book on Python (there are more apearing every day).

Put another way: when I make changes to the product, do I have to re-install it to get those changes to kick in?

No, when you change a class attribute (sometimes called a 'shared instances attribute), all instances will get that attribute. -Michel