Database systems, methods and/or computer program products provide for multiple but exclusive relationships between tables in a relational database. The multiple but exclusive relationship may be enforced based on a type associated with a record in a relating table. The multiple but exclusive relationship...http://www.google.de/patents/US7693845?utm_source=gb-gplus-sharePatent US7693845 - Database systems, methods and computer program products using type based selective foreign key association to represent multiple but exclusive relationships in relational databases
