In some cases, you can also expose in some ways the database schema to the user through a custom made ORM. The result is also a nightmare, it makes for really

In some cases, you can also expose in some ways the database schema to the user through a custom made ORM. The result is also a nightmare, it makes for really difficult upgrades, and a complex product for the customer as he has to have some database knowledge and can shoot himself in the foot quite easily. I still don't know which approach is the worst between EAV and exposing the data schema...