Object-Oriented Databases

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Requirements

• The structure of objects to be modeled can be nested.


• Object identity is supported to allow objects to be distinguished independently of their attributed values.


• Objects can be equipped with behavior which links specific operations exclusively to these entities.


• The structure and behavior of objects can be inherited hierarchically.


• The structure and the behavior definitions are extensible; that is, after completion of the database design new attributes and new operations can be defined and added to existing set.

The Paradigm of Object Orientation
Object orientation is based on the following five principles:

1. Each entity of a given application is modeled as an object with its own identity, which is different from the value of the object.
   
   

   Objects may be composed of other objects and objects may be referenced from several other objects (object sharing).



2. Each object encapsulates structure and behavior.
   1. Instance variables (attributes) give the structure of an object.
   2. An object’s set of values constitutes the state of the object.
   3. The behavior of an object results from the methods which can be executed on the object.