[Zope] Products vs. ZClasses- Design Question

[Garrin Kimmell]

Hello,

I would like some thoughts on design strategies for Zope classes. I am
developing a site that will require writing some custom classes. I would
appreciate any opinions anyone could offer. I apologize for such a long
message.

My class will have some instance variables along with some standard Zope
subobjects. My principal concern is that, because the graphical design of
the site is still in development, I will probably be making lots of
changes to the user interface of the class. I will want those changes to
be propogated to existing instances of the class. The underlying logic,
however, should be fairly stable.

I've thought of three ways to develop the class:

1. Develop the entire class as a Zope product in Python.

The advantage I see here is that developing the application logic is
fairly straightforward with Python. I see problems, though, with the
user interface, especially if I want to make changes to it after
instantiating a few objects. It is my understanding that objects created
from a Product are not automatically updated when changes are made to
the class methods (as opposed to ZClasses, where they are). Am I correct
here?

2. Develop the entire class as a ZClass

The principal advantage I see is that changes to the class
methods are dynamically updated in all instances of that ZClass. The
problem is that DTML is (for me, at least) a pain in the ass to write any
complicated application logic with.

3. Develop the application logic as a Product in Python, then use that
class as a mix-in class for a ZClass that implements UI logic with dtml
methods. 

This seems to be the best solution (even if it is the most work). I should
get the advantage of having ZClass instances automatically update changes
to ZClass methods, while having the programability of Python for 
application logic in the Product. If I do take this route, are there any
quirks I should be aware of when inheriting a ZClass from a product?


I am new to Zope and would appreciate any insight into the tradeoffs
among these three strategies. 

Thank you,
Garrin