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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In simple terms, Aggregation is a process when relation between two entities is treated as a single entity. In generalization, a number of entities are brought together into one generalized entity based on their similar characteristics.

Generalization, Specialization and Aggregation Concepts in DBMS

In generalization, some entities are accommodated together into one generalized entity or category based on their similar characteristics. Aggregration is a process when relation between two entities is treated as a single entity.

The reflection is the instrument used to shroud the unnecessary points of interest of an arrangement of articles. It breaks an entity into multiple entities from higher level super class to lower level sub class. In basic terms, Generalization is a procedure of removing normal attributes from two or more classes and joining them into a summed up superclass. It’s more like Superclass and Subclass system, but the only difference is the approach, which is bottom-up.

Various semantic data models have been proposed, and some of the most important semantic concepts have been successfully incorporated into the original ER model. Specialization is a process of identifying subsets of an entity that shares different characteristics.

Specialization is the opposite of generalization. A relationship represents a connection between two entity types that are conceptually at the same level. Specialization is the abstracting procedure of acquainting new qualities with a current class of items to make one or all the more new classes of articles. In basic terms, a gathering of substances in specialization can be classified into sub-bunches in view of their attributes.


Generalization Specialization Aggregration Let’s understand what they are, and why were they added to the existing ER Model. Generalization Generalization is a bottom-up approach in which two lower level entities combine to form a higher level entity.

The Enhanced ER Model

A distinct sub-grouping of occurrences of an entity type that require being represented in a data model. An entity type that includes one or more dissimilar sub-groupings of its occurrences that is required to be represented in a data model.

The normal qualities implies here properties or techniques. In specialization, a group of entities is divided into sub-groups based on their characteristics. For example, Saving and Current account types entities can be generalised and an entity with name Account can be created, which covers both.

Speculation Aggregatiob is the opposite procedure of Generalization Collection Generalization in DBMS Speculation is an abstracting procedure of review sets of items as a solitary general class by focusing on the general attributes of the constituent sets while stifling or overlooking their disparities. But in a company, persons can be identified as employee, employer, customer, or vendor, based on what role they play in the company. Hence, as part of the Enhanced ER Modelalong with other improvements, three new concepts were added to the existing ER Model, they were: C Tutorials C Programs.

The reverse is called specialization where a person is a student, and that student is Mira. The relationship between a superclass and a subclass is one-to-one 1: Specialization is opposite to Generalization. As the basic concepts of ER modeling aggregatioh often not enough to represent the requirements of the newer complex applications which therefore stimulated the need to develop additional ‘semantic’ modeling concepts.


In this chapter, you will learn about the main two important concepts. 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. Answered on 24th Jul,95 Views. It is a top-down approach in generalizaion one higher level entity can be broken down into two lower level entity.

An example of aggregation is the ‘Teacher’ entity following the ‘syllabus’ entity act as a single entity in the relationship.

The ER Model has the capability of articulating database entities in a conceptual hierarchical manner. As the specializaion of data increased in the late s, it became more and more difficult to use the traditional ER Model for speicalization modelling. Sometimes you may want to model a ‘has-a,’ ‘is-a’ or ‘is-part-of’ relationship, in which one entity represents a larger entity the ‘whole’ that will consist of smaller entities the ‘parts’.

The concept of generalization specialization is associated with special types of entities known as superclasses and subclasses, and the process of attribute inheritance. Notation of Generalization Generalization is represented by a triangle with a line.

Generalization Aggregation

In generalization, the higher level entity can also combine with other lower level entities to make further higher level entity. Going up in this structure is called generalizationwhere entities are clubbed together to represent a more generalized view.

The entity that is created will contain the common features. It allows lower-level entities to inherit the attributes of higher-level entities.