Door: a Dynamic Object-oriented Data Model with Roles

Traditional object-oriented programming languages do not support the dynamic type change of an object so as to model the behavior of real world entities which change their status over time. This is a severe limitation in the context of a database programming language. Moreover, traditional object-oriented languages do not model the fact that the behavior of real world entities may depend on the role that they play. This paper describes the data model for DOOR, a dynamic object-oriented database programming language with role extension, which addresses these problems. We distinguish object classes from role classes by de ning roles (instances of role classes) as parts of objects (instances of object classes). Objects are represented by globally unique and unchangeable identi ers while roles are represented by the names of their role classes as well as their values. The data model described in this paper emphasizes the role representation as well as the player quali cation for the role players.