1. Use Case Diagrams
Week 1 – Lab 1

2. What is a Use Case Diagram?
Explains what the main functionality of the system is
Mainly cares for the system’s expected behavior (what) rather that how it is done!

3. Use Case Diagram: Components
1) Actors
An actor specifies a role that some external entity adopts when interacting with the system directly.
It may represent a role played by:
a user
another system
a piece of hardware
Actors may be both at input and output ends of a use case

4. Use Case Diagram: Components
Describes all the services required or performed by the actor.

5. Example 1
Construct a use case diagram for a library management system. The system is used by the librarian, the assistant librarian and the clients.
The librarian, can add books, delete books, add clients, delete clients, list books, list clients, check in/out books
The assistant librarian has all the functionality of the librarian except for add/delete for books and clients
Clients may only check in/out books

6. Example 1 - Continued To find the actors  Look for nouns
To find the user case  Look for verbs

7. Example 1
Construct a use case diagram for a library management system. The system is used by the librarian, the assistant librarian and the clients.
The librarian, can add books, delete books, add clients, delete clients, list books, list clients, check in/out books
The assistant librarian has all the functionality of the librarian except for add/delete for books and clients
Clients may only check in/out books

9. Example 2
Construct a use case diagram for an online travel agency system. A new user can create a new profile with a username and a password. This profile can be changed at any time if the user wants. The user logs to the system using his/her username and password.
After logging into the system, the user inquires about different flights. The user can book, change or cancel a flight reservation. This includes choosing a payment method, and making a payment.