Thanks for the reference. Now I understand but I have rarely seen this pattern. As a DBA with 20 years experience I want as much data integrity in the database as possible but I think some business rules are more understandable in application code than in tables and foreign keys. I apologize that I do not have more time to study your model in detail but the business rule that only people in a department may access a database owned by the department does not require data to be persisted. I think it is easier in the application get the department of the user logged into the system and then allow access to database owned by the department. The information in the lower tables in your diagram have data that does not need to be persisted since it is easily inferred from data in the top tables.