Thirsty!
uc [package] Core use cases [buy soft drink]
Customer
Buy soft drink
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this information triggered a use case. The direction of the information fl ow is normally
from the system to the actuator. Look for the start of the fl ow in which the
actuator participates. If you fi nd it you ??™ ve found the pertaining use case.
If the actor is a sensor, it can be the trigger of a use case. However, the sensor
is not interested in the result of the use case. This means that we cannot describe
that use case from the sensor ??™ s view. Look for the actor or stakeholder that is
interested in the result, and formulate the use case from its view. If you can ??™ t fi nd
anything or anybody, you can omit that use case. Nobody will notice it ??™ s not there.
Or will they? If so, you ??™ ve found the interested party.
We now want to apply these heuristics to our system. We fi nd the information
fl ow PIN from customer to system ( Figures 2.23 and 2.24 ) in the system context
model of our system. Does the PIN input trigger a new fl ow in the system? We
will just assume it does in case of doubt.
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