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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Since the s there has been a rapid amplification in the development of many new database systems that have abgregation demanding database requirements than those of the traditional applications. 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. Various semantic data models have been proposed, and some of the most important semantic concepts have been successfully specialisation into the original ER model.


In this chapter, you will learn about the main two important concepts. The concept of generalization specialization is associated with special types of entities known as superclasses and subclasses, and the process of attribute inheritance. The ER Model has the capability of articulating database entities in a conceptual hierarchical manner. As the hierarchy goes up, it generalizes the view of entities, and as you go deep in the hierarchy, it will provide with the detail of every entity included.

Going up in this structure is called generalization, where entities are associated together to represent a more generalized view. A generalization is a bottom-up approach.

Generalization Aggregation

In generalization, some entities are accommodated together into one generalized entity or category based on their similar characteristics.

In the below-mentioned figure, whale, shark, and dolphin are generalized as fish, i. An entity type that includes one or more dissimilar sub-groupings of its occurrences that is required to be represented in a data model.

A distinct sub-grouping of occurrences of an entity type that require being represented specialziation a data model. The relationship between a superclass and a subclass is one-to-one 1: A relationship represents a connection between two entity types that are conceptually at the same level.


Generalization, Specialization and Aggregation Concepts in DBMS

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’. This special kind of relationship is termed as an aggregation.

Aggregation does not change the meaning of navigation and routing across the relationship between the whole and its parts. An example of aggregation is the ‘Teacher’ entity following the ‘syllabus’ entity act as a single entity in the relationship.

In simple words, aggregation is a process where the relation between two entities is treated as a single entity. C Tutorials C Programs.

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