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Last Updated: Dec 31, 2023
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Difference between Generalisation and Specialization in DBMS

Author Ankit Kumar
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Dbms - Database management systems
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Introduction

In database management systems (DBMS), generalization and specialization are two important concepts in entity-relationship modeling. Generalization involves creating a more general entity from multiple, more specific entities, forming a hierarchical structure. 

Specialization, on the other hand, is the process of refining a general entity into more specialized sub-entities, allowing for the representation of unique attributes or behaviors. Together, they enable the modeling of complex data structures, fostering data organization, inheritance, and flexibility in database design. In this article, we will learn about the Difference between Generalisation and Specialization in DBMS.

Generalisation and Specialization in DBMS

 

What is Generalization in DBMS?

In generalization, we group two or more low-level entities to form high-level entities. We know several entities may have many common attributes. We take their union and thus create a higher entity with all the specific qualities linked. All the different attributes will get connected to the particular entity.

It's a bottom-to-top approach, and it helps to reduce the size and complexity of the schema.

Let us look at an example for this, making it clearer to understand.

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Characteristics of Generalization in DBMS

  • Hierarchy: Generalization establishes a hierarchical structure, organizing entities into supertypes and subtypes.
     
  • Inheritance: Subtypes inherit attributes and relationships from their supertypes, promoting data consistency.
     
  • Specialization: It allows the customization of subtypes to represent unique properties or behaviors.
     
  • Completeness: Generalization can be total (mandatory) or partial (optional) regarding subtype assignment.
     
  • Polymorphism: It supports polymorphic relationships, facilitating versatile querying and data manipulation.

Example

Let us take two low-level entities as Car and Bus, and these two will have many common attributes and some specific attributes. And We will generalize and link the common attributes to the newly formed high-level entity named Vehicle.

Following is the diagram for this.

generalization diagram

The above diagram generalizes the Vehicles Car and Bus,  forming a new entity called Vehicle and linking the common attributes with it.

Let us now understand the concept of specialization.

Also read, File System vs DBMS

What is Specialization in DBMS?

It can be understood as the reverse of generalization. It is a top to down approach and increases the schema's size. In specialization, any superclass is further divided into subclasses based on its characteristics. The concept of inheritance is somewhat similar to a specialization.

Let us understand this more clearly with an example.

Characteristics of Specialization in DBMS

  • Customization: Specialization allows the creation of specific subtypes tailored to unique attributes or behaviors.
     
  • Hierarchy: Subtypes can have further subtypes, forming a hierarchical structure.
     
  • Inheritance: Subtypes inherit attributes and relationships from their supertypes, minimizing redundancy.
     
  • Mutual Exclusivity: Subtypes can be mutually exclusive, meaning an entity belongs to only one subtype.
     
  • Overlapping: Subtypes can overlap, permitting entities to belong to multiple subtypes simultaneously.

Example

For an entity Businessman in an income management system, we can further specialize it into other entities like Contractor and Shopkeeper. The common attributes will get linked to the entity Businessman, whereas the specific qualities will be connected to the Contractor and Shopkeeper.

Let us now look at the diagram for a more precise understanding of specialization.

specialization diagram

This diagram explains the concept of specialization.

Now we will look at the last yet essential topic  Aggregation in DBMS

Major Difference between Generalisation and Specialization in DBMS

The difference between Generalization and Specialization are:-

Generalization in DBMS

Specialization in DBMS

Generalization is the process of defining a higher-level entity that encompasses two or more lower-level entities that share common attributes or characteristics. Specialization is the process of defining one or more sub-entities from a single entity.
The purpose of generalization is to simplify the database structure by grouping similar entities into a more generic entity.  The purpose of specialization is to divide a more generic entity into more specific entities that have unique attributes or characteristics. 
An example of generalization in an employee database is to define a more generic entity called "employee" that includes all types of employees such as managers, clerks, and executives. An example of specialization in the same database would be to divide the "employee" entity into sub-entities such as "manager," "clerk," and "executive."

Click here to know about IEnumerable vs IQueryable

Frequently Asked Questions

What is specialization and generalization in DBMS?

Specialization and generalization in DBMS are modeling techniques. Specialization refines entities into subtypes, while generalization groups entities into supertypes, promoting data organization and inheritance.

What is an example of specialization?

An example of specialization in a DBMS is dividing a general "Vehicle" entity into subtypes like "Car," "Truck," and "Motorcycle," each with unique attributes.

Conclusion

We read about Generalization, Specialization, and Aggregation concepts in the article. We dived deep into the concepts through one example of each. We saw how these techniques are essential in today's scenario of creating humongous databases. A traditional E-R Diagram can make things complicated for such large databases. For our relief, we use the Enhanced-Entity-Relationship Model. Using the techniques can make our diagram more organized.

NInjas! You have taken the most crucial step in learning about the ER Diagrams.

Also Read - Cardinality In DBMS, Four Pillars of OOPS and What is schema in dbms

Do not stop here and learn all of the most required topics that will help you ace the placement interviews by joining our courses and checking Coding Ninjas Studio. You should check out the following list of top 100 questions to improve your knowledge of  SQL.

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