Here is a list of data abstraction concepts and their variants in EER model:
* Classification and instantiation - The EER variant of classification is represented by classifying entities into entity types based on their attributes and relationships. Relationship instances becomerelationship types. Forthe need offurther classification, we introduce superclass /subclass concepts and sometimes even categories. In EER model, there is no handling of class exceptions and no showing of examples (instances).
* Identification - EER model implements identification hy sticking
to the rule of name uniqueness. Every entity type, relationship type, attribute, subclass, superclass and category has to have unique name that no other object in database has.
* Specialization and Generalization - The concept of specialization and generalization in the EER model is represented by subclasses.
They are more specific objects than their respective superclasses and arerelated to them by IS-A-SUBCLASS-OF (or shortly IS-A) relationship.
* Aggregation and Association - EER schema uses aggregation
abstraction in form of creating new compositeobjects. We can aggregate attributes to createa composite attribute, entity type or even a relationship type if there’s need to. Association in EER modeling is simply a relationship type between two or more independent entity types.
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