The domain/key normal form is achieved when every constraint on the relation is a logical consequence of the definition of keys and domains, and enforcing key and domain restraints and conditions causes all constraints to be met.
General constraints however would normally require special database programming in the form of stored procedures (often of the trigger variety) that are expensive to maintain and expensive for the database to execute.
There is a constraint linking Wealthy Person Type to Net Worth in Dollars, even though we cannot deduce one from the other.
The DKNF violation could be eliminated by removing the Wealthy Person Type column.
Relationships that are impossible to express as foreign keys are obvious violations of DKNF.