> but I still have my head too wrapped around the relational model. I am
trying to build a simple application just to learn the basics of Durus,
but everything seems so deceptively simple. I keep wondering if there is
something I'm missing.

Welcome to the list, and the club ("seems so deceptively simple"). I felt
that way after first looking at ZODB and Durus years ago as I'd been
working with software based on RBDMS persistence for more than a dozen
years at the time. I remember feeling dis-join-ted (pardon the sql pun)
and uncomfortable. Rest assured this will pass, the feeling is only
temporary.

My advice would be to focus on modelling your application objects as
classes and force yourself to keep thinking in simple terms. Try to avoid
thinking about indexing for now; in time you may find as I did that you
end up needing far fewer indexes than you might currently imagine, and in
these early days of exploring what can be done with Durus for Python
object persistence, dwelling on indexing will only serve to keep you
thinking in sql-speak. Persistent objects and containers will get you a
long way.

    people = {}

    class Person:
        def __init__(self, id):
            self.id = id
            self.subscriptions = []

    class Subscription:
        # ...

    mw = Person()
    people[mw.id] = mw
    mw.subscriptions.append(Subscription('Some Magazine'))

    # query
    mw.subscriptions # returns all the person's subscriptions

I bet your perception that it "seems simple" is thanks to your own
realization that you can do an awful lot with basic Python objects like
lists and dictionaries (I've not used the persistent versions above just
for clarity).

We've done above the equivalent of defining and creating two SQL tables, a
foreign key relationship, insert the Person row, the related Subscription
row, and queried the subscription table for rows belonging to the 'mw'
Person.

I would recommend reviewing the Keep and User code in QP itself and then
perhaps look at a more complete implementation of User management in the
Dulcinea package David referred to.