This article will address the topic of Enhanced entity–relationship model, a matter of great relevance and interest today. Enhanced entity–relationship model has captured the attention of experts and the general public due to its impact on various areas of society. Along these lines, different aspects related to Enhanced entity–relationship model will be examined, from its origin and evolution, to its implications in the contemporary world. The opinions and positions of specialists in the matter will also be analyzed, as well as the possible solutions or measures to be taken regarding this issue. Without a doubt, Enhanced entity–relationship model is a topic that leaves no one indifferent, so it is essential to deepen its study and understanding to achieve a more complete and clarifying vision.
The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases.
It was developed to reflect more precisely the properties and constraints that are found in more complex databases, such as in engineering design and manufacturing (CAD/CAM), telecommunications, complex software systems and geographic information systems (GIS).
The EER model includes all of the concepts introduced by the ER model. Additionally it includes the concepts of a subclass and superclass (Is-a), along with the concepts of specialization and generalization. Furthermore, it introduces the concept of a union type or category, which represents a collection of objects that is the union of objects of different entity types. The EER model also includes EER diagrams that are conceptual models that accurately represent the requirements of complex databases.
Entity type Y is a subtype (subclass) of an entity type X if and only if every Y is necessarily an X. A subclass entity inherits all attributes and relationships of its superclass entity. This property is called the attribute and relationship inheritance. A subclass entity may have its specific attributes and relationships (together with all the attributes and relationships it inherits from the superclass). A common superclass example is a Vehicle superclass along with the subclasses of Car and Truck. There are a number of common attributes between a car and a truck, which would be part of the superclass, while the attributes specific to a car or a truck (such as max payload, truck type...) would make up two subclasses.
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Textbooks discussing EER and implementation using purely relational databases:
Booklet discussing EER and implementation using object-oriented and object–relational databases:
Textbook discussing implementation in relational and object–relational databases:
Shorter survey articles: