[Zope-DB] Example for RDB persistency in zope products?

[Nick Bower]

Does anyone have any examples of how I code relational database
persistency into an object (at a Zope product level)?

I've an application written to view and manage complex organisational
data in Python scripts, ZPTs and ZSQL methods, and would like to move it
to the product level and into persistent object land.  However, the RDB
persistency aspect is what I'm most confused about.

I've seen people talk about doing the following:

1. Inherit from ZSQL methods for their business objects
2. Call ZSQL methods from their business object logic
3. Using an existing DA, such as psycopg, directly, bypassing ZSQL
methods, and calling the DA connection methods from business logic
4. Writing their own DA for integration with business logic

3. would have seemed to me like the practical way to go, but I'm just 
not sure where to start for lack of documentation promoting any way 
other than using ZSQL.

Nick