Generalization, Specialization and Aggregation in ER Model – GeneralizationGeneralization is a process of generalizing an entity which. Generalization Aggregation – Learn DBMS in simple and easy steps starting from its The reverse is called specialization where a person is a student, and that. Generalization Aggregation – The concept of generalization (specialization) is associated with special types of entities known as superclasses and subclasses, .

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It is a top-down approach in which one higher level entity can be broken down into two lower level entity. In simple words, aggregation is a process where generalizattion relation between two entities is treated as a single entity.

The details of entities are generally hidden from the user; this process known as abstraction. It breaks an entity into multiple entities from higher level super class to lower level sub class.

Generalization, Specialization and Aggregation Concepts in DBMS

A relationship represents a connection between two entity types that are conceptually at aggrebation same level. The entity shall be a student, and further, the student is a person. In generalization, a number of entities are brought together into one generalized entity based on their similar characteristics.

In the below-mentioned figure, whale, shark, and dolphin are generalized as fish, i. Going up in this structure is called generalizationwhere entities are clubbed together to represent a more generalized view. Speculation is an abstracting procedure of review sets of items as a solitary general class by focusing specixlization the general attributes of the constituent sets while stifling or overlooking their disparities.


The reflection is the instrument used to shroud the unnecessary points of interest of an arrangement of articles. In generalization, some entities are accommodated together into one generalized entity or category based on their similar characteristics.

Spceialization mentioned above, the process of generalizing entities, where the generalized entities contain the properties of all the generalized entities, is called generalization.

Generalization, Specialization and Aggregation in ER Model | Studytonight

These properties are common in all persons, human beings. The reverse is called specialization where a person is a student, and that student is Mira. Aggregation represents relationship between a whole object and its component. Generalization is a Bottom up process.

Specialization speciallization opposite to Generalization. Notation of Generalization Generalization is represented by a triangle with a line. The normal qualities specializatino here properties or techniques. We use all the above features of ER-Model in order to create classes of objects in object-oriented programming.

The ER Model has the dbma of articulating database entities in a conceptual hierarchical manner. As the hierarchy goes up, it generalizes the view of entities, and as we go deep in the hierarchy, it gives us the detail of every entity included.

Generalization Aggregation

Hence some improvements or enhancements were made to the existing ER Model to make it able to handle the complex applications better. For example, the attributes of a Person class such as name, age, and gender can be inherited by lower-level entities such as Student or Teacher. Comments Edit Question Edit Categories. This special kind of relationship is termed as an aggregation.


A generalization is a bottom-up approach. Ddbms, in a school database, persons can be specialized as teacher, student, or a staff, based on what role they play in school as entities. Conglomeration is the procedure of ordering data on an item, in this way abstracting a larger amount object.

Generalization, Specialization and Aggregation in DBMS

In basic terms, Generalization is a procedure of removing normal attributes from two or more classes and joining them into a summed up superclass. Such an entity-set is treated in the same manner as any other entity-set. Hence, entities are combined to form a more generalised entity, in other words, sub-classes are combined to form a super-class. In the diagram above, the relationship between Center and Course together, is acting as an Entity, which is in relationship with another entity Visitor.

Aggregation does not change the meaning of navigation and routing across the relationship dbmw the whole and its parts.