Allow the user to modify and delete objects and relationships when they are no longer required In this case the system automatically maintains the integrity of objects, possibly using inverse attributes. For example, in Figure 25.11 we have a relationship from Branch to Manager and an inverse relationship from Manager to Branch. When a Manager object is deleted, it is easy for the system to use this inverse relationship to adjust the reference in the Branch object accordingly. The Ontos, Objectivity/DB, and ObjectStore OODBMSs provide this form of integrity, as does the ODMG Object Model (see Section 27.2).