An object oriented data model for distributed office applications

The object-oriented paradigm is becoming very popular for database applications and several object-oriented DBMSs have been developed. A basic notion in this paradigm is the inheritance hierarchy that allows the users to define objects and the associated operations starting from already defined objects. However, in database applications the inheritance hierarchy must provide a conceptual modeling function, in addition to the re-usability function. Another important requirement is to provide support for data distribution in (possibly) heterogeneous environments. This means that object implementation may differ depending on the object location. This paper presents a model that decouples these two aspects, modeling vs implementation, by using the concept of abstract and implementation classes. An abstract class specifies properties and methods for a set of similar objects, like in other object-oriented data models. An abstract class is however independent of the object implementation and location. An implementation class defines the implementation of an abstract class. In our model an abstract class may have several implementations. This allows the user to provide different implementations for the same set of objects, without requiring the objects to change class.