Use Case Diagrams
• In order to signify
• Actors signify functions,
that's, a kind of user of
Use Case Diagrams
• Use cases signify the
sequence associated with
interaction with regard to a
kind of functionality,
summary associated with
• The use case model may be
the set of all use cases. It's a
total explanation from the
functionality of the system
and its environment
• An actor models an external entity that
convey using the system:
– External system
– Physical environment
• An actor has a unique name as well as an
• For Examples:
– Passenger: A person in the train
– GPS satellite: Provides the system along
with GPS coordinates
The use case signifies the class of
associated with functionality supplied
by the actual system as an event flow.
The use case includes:
• Unique name
• Participating actors
• Entry conditions
• Flow associated with events
• Exit problems
• Unique needs
Use Case Diagram: Example
Name: Purchase ticket
Participating actor: Passenger
• Passenger standing in front of
• Passenger has sufficient money to
• Passenger has ticket.
1. Passenger selects the number of
zones to be traveled.
2. Distributor displays the amount
3. Passenger inserts money, of at least
the amount due.
4. Distributor returns change.
5. Distributor issues ticket.
The <<extends>> Relationship
• <<extends>> relationships signifies
exceptional or even seldom invoked
• The exceptional event flows are
factored out of the main event flow
• Use cases signifies exceptional flows
can extend more than one use case.
• The actual path of the<<extends>>
relationship is to the extended use
The <<includes>> Relationship
• <<includes>> relationship
signifies behavior that's
factored from the use case.
• <<includes>> is actually
factored away with regard to
reuse, not really since it is
definitely an exception.
• The actual path of the
would be to the actual
utilizing use case (unlike
Use Cases are useful to
• Identifying needs
– New use cases usually create new specifications because
the system will be assessed as well as the layout will take
• Interacting along with customers
– Their notational simplicity can make use case diagrams a
good way with regard to developers to communicate with
• Generating test cases
– The collection of scenarios for a use case may suggest a
suite associated with test cases for those scenarios.
Use Case Diagrams: Summary
• The use case diagrams symbolize external behavior
• The use case diagrams are helpful because an
index to the use cases
• The use case explanations supply meat associated
with model, not the use case diagrams.
• All use cases need to being explained for the model
to be useful.
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