The document discusses the Entity-Relationship (E-R) data model, which is a semantic data model used for conceptual database design. It has three main components: entities, attributes, and relationships. Entities represent real-world objects like people, places, events or concepts. Attributes are properties of entities, like name or identification number. Relationships define how entities are connected or related to each other. The document defines different types of entities, attributes, relationships, and provides examples and symbols used to represent them in E-R diagrams.

1. Database
Management
System
Lecture - 5

2. Entity-Relationship
Data Model

3. E-R Data Model
A semantic data model, used for
the graphical representation of
the conceptual database design

4. Major Components
Entities
Attributes
Relationships

5. Entity
Term used to mean three
different meanings
 Entity type
 Entity instance
 Entity set

6. Entity Type
A name/label assigned to
items/objects that exist in an
environment and that have similar
properties
It could be person, place, event or
even concept

7. Entity Type
Distinguishable from other
entity types on the basis of
properties
Identified through abstraction
process
Different from External Entity

8. Entity Instance & Set
A particular object belonging to
a particular entity type
Entity Type: Employee
Entity Instance: M. Sharif
Entity Set: All employees

9. Types of Entity Types
Entity types can be classified into
regular/strong/independent ETs or
weak/dependent ETs

10. Weak Entity Types
An entity type whose instances
cannot exist without being linked
with instances of some other entity
type, i.e., they cannot exist
independently

11. Strong Entity Type
A strong/regular entity type is the
one whose instances can exist
independently, i.e., without being
linked to other instances
Strong ETs have their own identity

12. Naming Entity Types
Singular noun recommended
Organization specific names
Write in capitals
 Abbreviations can be used,
be consistent

13. Symbols
Regular Entity Type
Weak Entity Type
NAME
NAME
EMPPLOYEE DEPENDENTS
BOOK BOOKCOPY

14. Attribute
An attribute of an entity type is a
defining property or quality of the
instances of that entity type. Entity
instances of same entity type have
the same attributes. (e.g. Student
Identification, Student Name)

15. Domain of an Attribute
Every attribute has a domain
Set of possible values for an
attribute
The attributes in an entity set/get
the values from the same domain

16. Types of Attributes
Single vs composite
Single valued vs multi-valued
Stored vs derived

17. Symbols for Attributes
Each represented as an oval,
linked with an ET symbol

18. Symbols for Attributes
Simple
Composite
Multi-valued
Derived

19. Example
EMPLOYEE
empId empName
Experience
emp_Qual street
dateHired houseNo
address

20. Thanks

21. Database
Management
System
Lecture - 7