A data model for autonomous objects

Developments in distribution and networking of computing power raise questions about the feasibility of centralised control in an information system. At the same time the move towards information systems ranging over a number of different organisations brings us systems where central control is not desired. This asks for systems built of components that can function independently under local control only. A move towards autonomous components can also clearly be seen in the area of active databases. Rules are seen as part of the behaviour of objects or relations between objects. Following the encapsulation principle, this leads to encapsulation of all rules with objects. The definition of such an object is independent of other objects. To support these developments we defined the data model for autonomous objects proposed in this report. An autonomous object is an object with its own thread of control. The behaviour of an autonomous object is defined by methods, rules and dynamic constraints. The latter two refer to the complete history kept with the object. The semantics of a relation between objects is captured in relation objects. This enables us to represent arbitrary complex conditions on initiating and terminating relations and to have arbitrary actions taken on certain events. Dependent on the relations an object has, its capabilities will evolve. This is achieved through addons. An addon defines capabilities an object can be, temporarily, extended with. Structure is brought into the mass of objects at the instance level through the objects at the class level. Class objects occur for all object classes, relation object classes and addons. Their function as an object container enables the approach of groups of objects, for example for queries.