Experiment No.
1
Title: Drawing E-R Diagrams for Different Applications
Design and Analysis of Entity-Relationship (E-R) Diagrams for Real-World Applications
Aim
To understand and practice the design of E-R diagrams for various common applications
(e.g., E-commerce, Airline Reservation, Hotel Management) in order to model real-world
systems and their data relationships.
Objectives
To introduce the concept and importance of E-R diagrams in database design.
To identify entities, attributes, and relationships in real-world applications.
To construct well-structured E-R diagrams using standard notations.
To analyze and interpret E-R diagrams for different domains.
To develop foundational skills required for database system design.
Theory
What is an E-R Diagram?
An Entity-Relationship (E-R) Diagram is a visual representation of the entities, attributes,
and relationships in a database system. It helps to systematically analyze and design
databases by identifying:
Entities: Real-world objects (e.g., Customer, Product, Flight, Room).
Attributes: Properties or details of entities (e.g., Name, Price, Flight Number).
Relationships: Associations between entities (e.g., Customer books Flight).
E-R Diagram Notations
Component Symbol Use
Represents real-world objects with a
distinct existence (e.g., Customer,
Product). Each entity typically becomes
Entity Rectangle a table in the database.
Describes properties of entities (e.g.,
name, price). Each attribute maps to a
Attribute Ellipse column in an entity's table.
Relationship Diamond Shows how entities are linked or how
Component Symbol Use
they interact (e.g., "places", "books").
Maps to associations or foreign key
relationships in the database.
Primary Underline Identifies unique records in an entity
Key d attribute (e.g., customerID).
Not
explicitly
shown in
basic E-R;
denoted
through Used to link entities via relationships in
Foreign Key links a relational database.
Straight Connects entities to attributes or
Line line relationships.
Multi-
valued Double Represents attributes that can have
Attribute ellipse multiple values (e.g., phone numbers).
Shows attributes whose value can be
Derived Dashed derived from other attributes (e.g., age
Attribute ellipse from birthdate).
Steps in E-R Modeling
1. Requirement Analysis: Understand the application's functional requirements.
2. Identify Entities: List all distinct object types involved.
3. Determine Relationships: Specify how entities interact.
4. List Attributes: Assign properties to each entity.
5. Draw the Diagram: Use standard symbols to construct the E-R structure.
6. Review and Refine: Validate completeness and accuracy with use-cases.
Steps to Carry Out
1. Select the Application
o Example domains: E-commerce Store, Airline Booking, Hotel Reservation
2. Requirement Gathering
o List out the main functions and processes of the chosen application.
3. Entity Identification
o Note down primary entities (users, products, flights, rooms, etc.).
4. Attribute Listing
o Assign meaningful attributes to each entity (user ID, email, price, etc.).
5. Relationship Mapping
o Define how entities interact (e.g., Customer places Order).
6. Draft the E-R Diagram
o Use a drawing tool or paper to construct the diagram using correct notations.
7. Validation
o Cross-check against requirements; ensure all main scenarios are covered.
Example: put your own done example in lab session
Expected Outcomes
Ability to identify and represent entities, attributes, and relationships from real-world
application descriptions.
Skill to construct standard E-R diagrams for a variety of domains.
Understanding of normalization and relational mapping.
Foundational knowledge for further database design workshops and projects.
Enhanced ability to document and communicate data models professionally.
