The document discusses extended entity-relationship (E-R) models, which were developed as an enhancement to the traditional E-R model to better handle increasingly complex database applications. Four new concepts were added as part of the extended E-R model: generalization, which combines two lower-level entities into a higher-level entity using a bottom-up approach; specialization, which breaks a higher-level entity into two lower-level entities using a top-down approach; inheritance, which allows lower-level entities to inherit attributes from higher-level entities; and aggregation, which treats the relationship between two entities as a single entity. Examples are provided to illustrate generalization and specialization.

1. Extended E-R Model
Prepared By:
Mr. Sanjay Kumar
Assistant Professor (ITD)
Rajkiya Engineering College, Azamgarh
SANJAY KUMAR September, 2020 1

2. Extended Entity-relationship Models
 Extended entity-relationship models, also known as Enhanced entity-
relationship models– It is advanced database diagrams very similar to
Regular E-R diagram.
 As the complexity of data increased in the late 1980s, it became more and
more difficult to use the traditional ER Model for database modelling.
 Hence some improvements or enhancements were made to the existing ER
Model to make it able to handle the complex applications better
SANJAY KUMAR September, 2020 2

3. .
 Hence, as part of the Enhanced ER Model, along with other
improvements, four new concepts were added to the existing
ER Model, they were:
1. Generalization
2. Specialization
3. Inheritance
4. Aggregation
SANJAY KUMAR September, 2020 3

4. Generalization
 Generalization is a bottom-up approach in which two lower
level entities combine to form a higher level entity.
 Generalization is a process of generalizing an entity which
contains generalized attributes or properties of generalized
entities.
 It's more like Superclass and Subclass system, but the only
difference is the approach, which is bottom-up.
SANJAY KUMAR September, 2020 4

5. Example:
SANJAY KUMAR September, 2020 5

6. Specialization
 Specialization is opposite to Generalization.
 It is a top-down approach in which one higher level entity can
be broken down into two lower level entity.
SANJAY KUMAR September, 2020 6

7. SANJAY KUMAR
September, 2020 7

8. Example:
SANJAY KUMAR September, 2020 8

9. Inheritance
 Inheritance allows lower-level entities to inherit the attributes
of higher-level entities.
SANJAY KUMAR September, 2020 9

10. Aggregation
 Aggregation is a process when relation between two entities is
treated as a single entity.
SANJAY KUMAR September, 2020 10

11. THANK YOU
SANJAY KUMAR September, 2020 11