1. Use Cases -Use Case Diagram
Chapter 3

2. Outline Use Case – defined Techniques for Identifying Use Cases
User Goal
Event Decomposition
CRUD
UML's Use Case Diagram

3. Use Case - Defined Use case - an activity that the system performs
usually in response to a request by a user
Functional Requirements
Verb + Noun
Place order
Issue complaint
Techniques to Identify use cases:
User Goal
Event Decomposition
CRUD

4. Identifying Use Cases- User Goal Technique
Ask the users what they need the system to do
Identify the users
Interview them
Create the list of use cases
Some users may need the same use case
Watch out for duplicates, inconsistencies
Verify the list with the users

5. Identifying Use Cases- Event Decomposition
Identify the events that occur to which the system must respond.
Event - an occurrence at a specific time & place which needs to be remembered
Use Case - what the system does when the event occurs
Prior Conditions & Events

6. Identifying Use Cases- Event Decomposition
Types of Events
External
Temporal
State

7. Identifying Use Cases - CRUD Analysis
Can be a tool for: use case identification and/or validation
Ensure that there are use cases to cover the CRUD
CRUD - For 1 data entity C R U D
CRUD Matrix
All use cases
All data entities
Shows responsibilities

8. CRUD CRUD Use Cases Cancel order Place order Change order
Update customer profile
Print order report
View order status …
Order C
Create R
Read U
Update D
Delete
CRUD Matrix
Use Cases
Order
OrderItem
Customer
Item
Place Order
Update Customer Profile …

9. UML's Use Case Diagram

10. UML - The Unified Modeling Language
An Object-Oriented modeling language
"3 Amigos" - Booch, Rumbaugh, and Jacobson
Adopted & now managed by OMG (Object Management Group)
Models both structure & behavior
Structure diagrams
Class diagram, Component diagram, Deployment diagram, Object diagram, Package diagram, etc.
Behavior diagrams
Activity diagram , Use Case diagram , Sequence diagram, State machine, Communication diagram, etc. 10

11. <<system>>
Use Case Diagram
A UML diagram depicting the relationship between actors & use cases
Defines Scope/Functional Requirements
Automation Boundary
The boundary between the software and the actors of the system
Actor
Anyone or thing that interacts with the system
Use Case
an activity that the system performs
Association
Depicts a usage relationship between an actor and a use case
<<include>> & <<extend> Associations
Customer
Billing
<<system>>
Time
<<include>>
<<extend>>

12. Use Case Diagram - Sales Subsystem
Prefer "Place an order"

13. Use Case Diagram – ATM System
Withdraw
cash
Customer

14. Use Case Diagram – Order Entry System
Customer
Sales
clerk
Create new order
Lookup
item availability
Update order
Order Entry System

15. <<include>>
Customer
Sales
clerk
Create new order
Lookup
item availability
Update order
Order Entry System
Authenticate
customer
<<include>>
This also
achieves
Reuse!
<<include>>

16. <<extend>>
Customer
Sales
clerk
Create new order
Lookup
item availability
Update order
Order Entry System
This also
achieves
Reuse!
Record
Authentication Issue
<<extend>>
Authenticate
customer
<<include>>
<<include>>
Suggest
substitute items
<<extend>>
<<include>>

17. "Withdraw Cash” Use Case – i.e. scenario
Customer
Customer
ATM
Bank

18. <<Time>>
Special Use Cases
State-driven use cases
e.g. Polling, Monitoring, Notifications
Time-based Use Cases
Employee
Reorder
Stock
<<Time>>
Generate
Payroll