[Zope] List attribute inside of a product...

I'm writing a product that needs a list of items inside it, e.g ['abc', '456', '243']. The list stays intact if the server is up. But if I shutdown and restart, the list is cleared again. Here's some of my code: class Store(Folder.Folder, PortalContent, DefaultDublinCoreImpl): """ Store Class """ meta_type = 'Store' _isDiscussable = 1 icon = PortalContent.icon categoryList = [] def manage_addCategory(self, id, title, REQUEST = None): self.categoryList.append(id) Is this the reason my list is getting reset to empty on restart? I don't understand. If I have a text attribute and set it to empty in the class code, then it's fine. I get my saved attribute. But my list is blown away. Jeff