A generalization hierarchy is an Inheritance re-presentation method that specifies common attribute of multiple entities into generalized or higher level entity type is called Super Type Entity and the lower level entity designed with unique attribute of each entity is called Sup Type Entity.
The General Entity is called Supertype (Parent) Entity and Special Entity is called Subtype (Child) Entity. Between these two different types of entities, we can define an inheritance link. In an inheritance link, one or more Subtype entities inherit, at the Physical Level, all or part of the attributes carried by one Supertype Entity.
The Supertype Entity is a generic entity type that is related to one or more Subtype Entities. Supertype Entity defines common characteristics attributes.
The Subtype Entity is a specific entity type that is related to one Supertype Entity. Subtype Entity defines unique characteristics attributes.
Overlapping Subtype Entity
Overlapping Subtype Entity defines non-unique characteristics attributes and related with more than one layer Supertype Entity.
Disjoint Subtype Entity
Disjoint Subtype Entity defines unique characteristics attributes and related with one Supertype Entity.
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