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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Hence, entities are combined to form a more generalised entity, in other words, sub-classes are combined to form a super-class.

Generalization, Specialization and Aggregation in ER Model

In specialization, a group of entities is divided into sub-groups based on their characteristics. A distinct sub-grouping of occurrences of an entity type that require being represented in a data model. Aggregration is a process when relation between two entities is treated as a single entity.

But in a company, persons can be identified as employee, employer, customer, or vendor, based on what role they play in the company. An example of aggregation is the ‘Teacher’ entity following the ‘syllabus’ entity act as a single entity in the relationship.

Specialization is a process of identifying subsets of an entity that shares different characteristics. The entity that is created will contain the common features. As the complexity of data increased in the late s, it became more and more difficult to use the traditional ER Model for database modelling. Specialization is opposite to Generalization. A relationship represents a connection between two entity types that are conceptually at the same level.

In generalization, a number of entities are brought together into one generalized entity based on their similar characteristics. Generalization Generalization is a bottom-up approach in which two lower level entities combine to form a higher level entity. In the diagram above, the relationship between Center and Course together, is acting as an Entity, which is in relationship with another entity Visitor.


For example, a particular student named Mira can be generalized along with all the students. For example, Saving and Current account types entities can be generalised and an entity with name Account can be created, which covers both.

This special kind of relationship is termed as an aggregation. So it is a top-down methodology in which one larger amount substance can be separated into two lower level element. Notation of Generalization Generalization is represented by a triangle with a line. A person has name, date of birth, gender, etc. In specialization, a higher level entity may not have any lower-level entity sets, it’s possible.

Generalization, Specialization and Aggregation in ER Model

Comments Edit Answer Report. Hence, as part of the Enhanced ER Modelalong with other improvements, three new concepts were added to the existing ER Model, they were: The entity shall be specializzation student, and further, the student is a person.

As the basic concepts of ER modeling are often not enough to represent the requirements of the newer complex applications which therefore stimulated the need to develop additional ‘semantic’ modeling concepts. Using aggregation we can express relationship among relationships.

The Enhanced Feneralization Model As the complexity of data increased in the late s, it became more and more difficult to use the traditional ER Model for speciialization modelling. In this way, the two deliberation instruments used to model data: The relationship between a superclass and a subclass is one-to-one 1: C Tutorials C Programs.

In this chapter, you will learn about the main specializatioj important concepts. The ER Model has the power of expressing database entities in a conceptual hierarchical manner. Comments Edit Question Edit Categories. Similarly, in a school database, persons can be specialized as teacher, student, or a staff, based on what role they play in school as entities.


Generalization, Specialization and Aggregation in ER Model | Studytonight

Would you like to add a better answer? The reverse is called specialization where a person is a student, and that student is Mira. Aggregation in DBMS Conglomeration is the procedure of ordering data on an item, in this way abstracting a larger amount object.

In generalization, the higher level entity can also combine with other lower level entities to make further higher level entity. It is a top-down approach in which one higher level entity can be broken down into two lower level entity. The reflection is the instrument used to shroud the unnecessary points dbmss interest of an arrangement of articles.

It is a form of abstraction that specifies two or more entities sub class having common characters that can be generalized into one single entity super class at higher level hiding all the differences. Speculation Specialization is the opposite procedure of Generalization Collection Generalization speciaalization 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 specializatuon disparities.

Inheritance is an agyregation feature of Generalization and Specialization. Such an entity-set is treated in the same manner as any other entity-set. We use all the above features of ER-Model in order to create classes of objects in object-oriented programming.