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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A relationship represents a connection between two entity types that are conceptually at the same level. An entity type that includes sppecialization or more dissimilar sub-groupings of its occurrences that is required to be represented in a data model. The reverse is called specialization where a genealization is a student, and that student is Mira. Going up in this structure is called generalization, where entities are associated together to represent a more generalized view.

Gdneralization example, Saving and Current account types entities can be generalised and an entity with name Account can be created, which covers both. Using aggregation we generalizxtion express relationship among relationships. The entity shall be a student, and further, the student is a person.

Conglomeration is the procedure of ordering data on an item, in this way abstracting a larger amount object. 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. 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.

Aggregration is a process when relation between two entities generalizatiin treated as a single entity.

Generalization, Specialization and Aggregation in DBMS

In simple words, aggregation is a process where the relation between two entities is treated as a single entity. Generalization is a process of generalizing an entity which contains generalized attributes or properties of generalized entities. Speculation is an abstracting procedure of review sets of items as a generalizatioj general class by focusing on the general attributes of the constituent sets while stifling or overlooking their disparities.


It allows lower-level entities to inherit the attributes of higher-level entities. As the hierarchy goes up, it generalizes the view of entities, and as we go deep in the hierarchy, it gives slecialization the detail of every entity included. A generalization is a bottom-up approach.

Generalization, Specialization and Aggregation in ER Model

We use all the above features of ER-Model in order to create classes of objects generalkzation object-oriented programming. In the below-mentioned figure, whale, shark, and dolphin are generalized as fish, i.

Specialization might be seen as the opposite procedure of Generalization. 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. 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.

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’. Comments Edit Answer Report. In this way, the two deliberation instruments used to model data: The concept of generalization specialization is associated with special types of entities known as superclasses and subclasses, and the process of attribute inheritance. Inheritance is an important feature of Generalization and Specialization.

Aggregation in DBMS Conglomeration is the procedure of ordering data on an item, in this way abstracting a larger amount object. So it is a top-down methodology in which one larger amount substance can be separated into two lower level element.

Generalization, Specialization and Aggregation in ER Model

Generalization Specialization Aggregration Let’s understand what they are, and why were they added to the existing ER Model. The details of entities are generally hidden from the user; this process known as abstraction.


Since the s there has been a rapid amplification in the development of many new database systems that have more demanding database requirements than those of the traditional applications. In specialization, a group of entities is divided into sub-groups based on their characteristics.

The ER Model has the capability of articulating database entities in a conceptual hierarchical manner. It is a top down approach in which we first define the super class and then sub class and then their attributes and relationships. In basic terms, a gathering of substances in specialization can be classified into sub-bunches in view of their attributes.

Various semantic data models have been proposed, and some of the most important semantic concepts have been successfully incorporated into the original ER model.

Aggregation does not change the meaning of navigation and routing across the relationship between the whole and its parts. Answered on 24th Jul,95 Views. Would you like to add a better answer? Aggregation represents relationship between a whole object and its component. Hence, as part of the Enhanced ER Modelalong with other improvements, three new concepts were added to the existing ER Model, they were: In the diagram above, the relationship between Center and Course together, is acting as an Entity, which is in relationship with another entity Visitor.

The reflection is the instrument used to shroud the unnecessary points of interest of an arrangement of articles. The relationship between a superclass and a subclass is one-to-one 1: In generalization, a number of entities are brought together into one generalized entity based on their similar characteristics. 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.