Such a fl ow does not correspond
to the standard defi nition of a use case. It has no external trigger and no
FIGURE 2-35
A use case called ??? start car usage. ???
FIGURE 2-34
A potential use case called ??? unlock car. ???
uc [package] Car usage [unlock car]
Customer data
Customer
Reservation
system
Unlock car
Usage right
uc [package] Car usage [start car usage]
Usage right
Reservation
system
Start car usage
Customer
Card data,
PIN
71
defi ned end result, but supplies results continually. So, if you want to describe a continuous
fl ow rather than just a traversal, you should use a continuous use case.
When does the use case show car usage data begin? What we need is mileage
information in order to determine the car usage data, which will form the basis for
customer billing later on. To ensure that customers can keep themselves updated
on the current state of costs incurred, this information is presented regularly on the
display unit??”similar to a taximeter. The display of usage data additionally includes
the usage time currently run up, and it will be shown even while the car is not
moving.
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