Dynamic knowledge representation in DOOR

In many class based, object oriented database systems the association between an instance and a class is both exclusive and permanent. Therefore, these systems have serious difficulties in representing objects taking on different and multiple roles over time, and hence cannot model the dynamic knowledge from the real world. The paper describes a novel object oriented database management system, called DOOR, which supports object evolution, dynamic role (context dependent) modeling, objects of multiple specific classes, and object role relationships. In DOOR, a role is an entity with state and behavior, but it does not have a globally unique identity. Therefore, its existence has to be associated with an object. A role acts as a special association between its owner and player, such that its owner can prescribe its state and its player gains its properties through dynamic role playing. In this way, an object can evolve dynamically and cooperatively according to its associated objects.