2. Definition of
use case
CONTENTS
Use Case
Symbols
Difficulties
With Use
Case
Diagram
Use Case
Elements
Use Case -
Relationships
Example Of
Use Case
Relationship
Building
Use Cases
Use Case
diagram-
Example
Purpose of
Use Case
Diagram
Benefits
Of Use
Case
Diagram
6. 03
02
01
Actor
Use
Case Element
s
The actor(s) who trigger the use
case to activate. An Actor is
outside or external the system.
It can be a:
• Human
• Peripheral device
(hardware)
• External system or
subsystem
• Time or time-based eventIt is represented by stick figure.
Actor
7. 03
02
01
Use Case
Use
Case Element
s
A use case in a use case diagram is a visual
representation of a distinct business
functionality in a system. A use case is a
summary of scenarios for a single task or
goal.
For example- The figure shows in below have
two use cases: "Make appointment" and
"Perform medical tests" in the use case
diagram of a clinic system.
Use case
Fig: Use cases in a use case
diagram
12. Child use case Parent use case
Generalization Relationship:
A generalization relationship is also a
parent-child relationship between use
cases. In a use case diagram, generalization
is shown as a directed arrow with a triangle
arrowhead. The child use case is connected
at the base of the arrow.
16. 01 Identify the major use cases
Activities: Start a use case form for each use case
If more than nine, group into packages
Step
02 Identify the major steps within each use case
Activities: For each use case, fill in the major steps
needed to process the inputs and produce the
outputs
Step
03 Identify elements within steps
Activities: For each step, identify its triggers
and its inputs and outputs
Step
04 Confirm the use case
Activities:
For each use case, validate
that it is correct and complete
Step
BUILDINGUSECASES
18. Developed by
analysts
together with
domain experts
Validate a
systems
architecture
Specify the
context of a
system
Defining and
organizing
functional
requirements
in a system
Drive
implementation
and generate test
cases
Capture the
requirements
of a system
PURPOSE OF USE CASE DIAGRAM
Use case diagrams are typically develop in
early stage of development and people
often apply use case modeling for the
following purposes:
19. 01
Detailing user
interaction goals with a
product
02
Use cases are determining
the specific needs of a project
03
Use cases provide a
contractual delivery
process
04
Use cases provide an easily
understood communication mechanism
05
Outlining and ensuring the
requirements of a system
06
Modeling the basic flow of
events in a use case
BENEFITS OF USE CASES
20. Require the co-existence
of prototypesNumber
04
They do not capture the non-
functional requirements easily
Number
03
Time-consuming
to generateNumber
02
Limited software
tool supportNumber
01
DIFFICULTIES WITH
USE CASES
Editor's Notes
System boundary: A system boundary defines the scope of what a system will be. A system cannot have infinite functionality. So, it follows that use cases also need to have definitive limits defined. A system boundary of a use case diagram defines the limits of the system. The system boundary is shown as a rectangle spanning all the use cases in the system.
Other use cases in this lecture also show the system boundary of the clinic application. The use cases of this system are enclosed in a rectangle. Note that the actors in the system are outside the system boundary.
The system boundary is potentially the entire system as defined in the problem statement. But this is not always the case. For large and complex systems, each of the modules may be the system boundary. For example, for an ERP system for an organization, each of the modules such as personnel, payroll, accounting, and so forth, can form the system boundary for use cases specific to each of these business functions. The entire system can span all of these modules depicting the overall system boundary.
Inheritance
A use case generalization shows that one use case is simply a special kind of another.
A clinic may have a use case such as Pay Bill which would be a parent use case and Bill Insurance which is the child.
A child can be substituted for its parent whenever necessary.
Generalization appears as a line with a triangular arrow head toward the parent use case.
