Generalization, Specialization and Aggregation, are data abstraction mechanisms in the ER model. They are useful to hide specifics of a set of objects.
Generalization in ER Model
This is similar to a bottom-up method. Here, generally two or more lower-level entities unite to generate a higher-level object. But they must share some features. In principle, an entity of a higher level can merge with entities of a lower level to generate a new entity of a higher level. The method to generalization is similar to that of the subclass and superclass systems. The bottom-up technique is useful in generalization. Entities can merge to generate a more generalized entity in generalization, i.e., subclasses can combine to form a superclass.
Specialization in ER Model
The antithesis of Generalization is Specialization, which is basically a top-down strategy. One higher-level entity can be divided into two lower-level entities by specialization. The term “specialization” basically is a subset of an entity collection that has some common properties. The superclass is typically defined first, followed by the subclass and its related properties, and finally the relationship set.
Aggregation in ER Model
An ER diagram cannot depict the relationship between an entity and a relationship, but it is necessary in some cases. A relationship with its relevant entities is basically aggregated into a higher level entity in these situations. Aggregation is a concept that allows us to express relationships as higher-level entity groupings. Create a schema that includes the following elements to represent aggregation.
1. the aggregated relationship’s primary key.
2. the associated entity set’s primary key.
3. If one exists, a descriptive attribute.
In the tutorial, we learned about the principles of generalization, specialization, and aggregation. Through one example of each, we delved deeply into the topics. We showed how important these strategies are in today’s reality of building massive databases. For example, in huge databases, a typical E-R Diagram can be confusing. We employ the Enhanced-Entity-Relationship Model for our relief. Using the strategies, we may improve the organization of our diagram.