[Zope] Relational queries on zope obj db?

[marc lindahl]

> From: "Jeff Kowalczyk" <jtk@adelphia.net>
> 
> A simple example would be: customer-class in one folder,
> purchaseorder-class in another, productitem-class in a third; select all
> purchase orders for customerA, displaying each individual productitem
> ordered.

Why would you have those three things in different folders?  Why not, for
example have:

class Productitem:
   def __init___
      price = 0
      itemno = 0
      upc = 0
      description = ''
      etc....

class Purchaseorder:
   def __init__
      ponumber = 0
      itemlist = []
      shipping = 0
      terms = 'net 30'
      tax = 0
      date = ZopeTime()
   def total(self)
      total = 0
      for i in itemlist
         total = total + i.price
      total = total * (1 + self.tax) + self.shipping
      return total
   etc...

def Customer:
   def __init__
      customerid = 0
      terms = 'net30'
      address = ''
      purchase_orders = []
      etc....


So then you instantiate a customer object for each customer (customer1 =
Customer()), and each time a purchase order is made you'd instantiate one of
those and add it to the list:
customer1.purchase_orders.append(Purchaseorder())
then you could add items to the last purchase order (of course, you'd
probably want to address it by name, easily done in python, but for
simplicity...)
customer1.purchase_orders[-1].itemlist.append(Productitem())

Seems the object orientation of python makes something like this the natural
organization, as opposed to the table orientation of a so-called RDB....

Then in Zope, you'd naturally take steps to Catalog these things as they
were created, facilitating high speed searches and report generation.