Use Cases
Week 8
CMIS570
Refresher – Class Diagrams
Appointment scheduling example
Car Rental example
E-Commerce example
UML diagrams
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9 diagrams
Used throughout SDLC
Use consistent syntax and notation.
Key building block is the use-case.
Use-Case
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Requires you to break system into use
cases, small logical pieces of the system
and deal with each separately.
In contrast, DFDs and ERDs encompass
the entire system in one diagram.
Use-Case Diagrams
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Graphical specification of the system’s
behavior from the perspective of the user(s).
Describes what the system does without
describing how the system does it.
They are used to identify and communicate
the high-level business requirements for the
system.
Use-Case contains:
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Actor
Event/Use Case
Association
System boundary
Example!
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Patient Admission system
Example
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Car Rental System
Another example
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E-commerce system
Steps in creating a Use-Case
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1. Identify use-cases (find major
functions)
2. Draw the system boundary
3. Place use-cases on the diagram (6-8
use-cases per diagram)
4. Identify the actors
5. Add associations
In addition…
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Text documents to document use-cases since
use-case diagram does not describe how
those use cases are carried out by the actors.
When describing the use-case, you should
focus on its external behavior – how it
interacts with the actors, rather than how the
use case is performed inside the system.
Steps in Documentation
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1. Create a use case template that has
areas labeled Basic Course and
Alternative Courses.
2. Ask “What happens?”
3. Ask “And then what happens?”
4. Ask, “What else can happen?
Documentation examples
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Patient Admission
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Rent a car
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Search by Author
TIPS
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Think usage scenario rather than
functional requirements.
Describe usage rather than attributes
and methods.
Don’t write use-case too tersely.
Don’t ignore system responses.
Don’t forget alternative courses of
action
Includes statement
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When one use-case needs to use
another use-case
Two types
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Internal – only other use-cases reference
Both external actors and internal use-cases
reference
Examples
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Order Entry
Class registration