Object Deputy Model and Its Applications

In this paper, the concept of object deputy model is introduced to realize flexible objectbases. The model was required to realize advanced database applications, such as geographic databases, virtual office systems and distant education systems which are currently developed in our group. The model can also treat well-known problems of object-oriented data models: realization of flexible views, objects with more than one role, object migration history and multiple inheritance. An object appearing in a view can be regarded as playing a role, object migration corresponds to role change history of an object and multiple inheritance realizes aggregation of object roles, thus these problems can be handled uniformally. A deputy object has attributes and methods not in the source object. It has own object identifier, attribute values computed from attribute values of the source object, and methods generated from these of the source object. Furthermore, deputy classes are also introduced. The model realizes generalized inheritance mechanisms. A model for distributed databases and knowledge bases, data-knowledge coordination model, can be regarded as a model to realize very flexible objectbases. It is shown that the object deputy model can simulate dataknowledge coordination model. Applications to geographic databases, virtual office systems and distant education systems are also discussed.