Object Oriented Databases with Django
Three times over my Django-programming career I've had this same problem. I have a highly polymorphic domain that I'm trying to represent to Django. As is well known in the world of RDBMSes, this leads to very large and complex sets of database tables with correspondingly slow lookup and heavy validation requirements.
Lets, for a simple example, imagine building an ecommerce solution for selling antiques. The antiques we have in stock all belong to one or more categories of antiques. So far so simple: an Antique model with a many to many relationship with a Category model. For each antique we need to store various bits of information: information on its quality, provenance, and damage. But, crucially, the information we need to store for each antique depends on its categories. So for a piece of furniture our shop browsers will expect certain information, while collectors of miniature paintings will expect others.
We could solve this problem by allowing each antique to have any number of properties, and then enter all the relevant information ourselves each time we put a new antique in the system. This would work, but be very error prone: we might forget a salient piece of data. It is also laborious, in most cases there are sensible defaults for propoerties that we'd do well to use. And it begs the question what data type do we store data in? Some properties might be dates, others quality levels, yet others names.
So we could create a fiendishly complex model where categories define certain required parameters, defining their default value and data type, and some flexible parameter table holds the paramaters that are non-default for a particular antique, in such a way that any data can be input (or maybe different parameter tables for different data types). It works but it is very inelegant and laborious to code.
There's got to be a better way.