2. What is a use case diagrams?
■ A requirements analysis concept
■ Use to collect requirements from
The customer
■ Describes the system's actions
from the point of view of a user
■ Represent system functionality
■ Interactions of a user with
the system
Used mainly in requirements document
What will the system do ?
3. Actors
■ They are the entities that interact with the system.
■ The people or systems that provide or receive
information from the system
actor
People
Computer
h/w &
devices
External
system
4. Types of actor
Primary actor Secondary actor
Primary actor
•They are completely outside the system
and drive the system requirements
Secondary actor
•They often appear to be more inside the
system than outside
5. How to Identify Actors?
■ Who benefits from several needs listed in the requirements?
■ Who will use the system?
■ In which organization will the system be located?
■ Who will provide the system with input data? Who will
use these data? Who will use output data? Who will maintain the
system?
■ Who will perform technical support onto the system?
■ Does the system use external resources?
6. Use case
■ A description of a set of sequences of actions, Use case
focuses on the goal of the functions.
■ Identifier the main functionalities of the system
7. How to identify use cases ?
■ What functionality should be included or excluded?
■ Relations between the system under analysis and other systems
■ Results and outputs produced by the system
8. Use Cases - Example
Make
Reservation
Cancel
Reservation
Modify Class
Print Ticket
Query
Timetable
Check Fare
Register
as Member
9. System boundaries
■ It defines the scope of the system being developed
and are represented by rectangles in uml notation.
10. Use case analysis may helpful in following areas:
■ Discovering new features(requirements):
– New use case often help generate new requirements as the
system is analyzed and as the design takes shape.
■ Communicating with the clients and development team:
– Their national simplicity makes use case diagrams a mechanism
for early discussion with potential users and domain experts.
■ Generating test cases:
– A use case is a generalized description or template of a sequence
of transaction, while a scenario is an instance of the use case
which describes how the use case will be executed in a specific
situation.
11. Uml notation for use case
Use case
Actor
System
boundary
Association
Generalization
Extend
Include
<<extend>>
<<include>>
12. Structuring use case with relationships
UML supports three types of
relationship for use case
<<include>>
<<extend>>
generalization
13. The <<include>> relationship
■ <<include>> relationship are used when two or
more use case share some common portion in
the flow of events.
Withdraw
money
Deposit money
Login account
<<include>>
<<include>>
14. ■ <<extend>> Specifies that the target use
case extends the behavior of the source
The <<extend>> relationship
Withdraw
money
Process extra
amount
<<extend>>
User
15. The generalization relationship
■ A child use case can inherit the behaviors, relationships and
communication links of parent use case.
■ The relationship between the child use case and the parent use case is
the generalization relationship.
Perform
Payment
Payment By
Credit Card
Payment By
CheckCustomer
