4). I intentionally chose these vague formulations because UML does
not make any specific statement about the trigger and result of a use case. You ??™ ll
learn how to handle exceptions in Section 2.4.
In addition to actors who are users, there can also be actors that a use case
requires in order to perform a service. It is typical especially for embedded systems
to have many actors connected with a use case.
A use case is denoted as an ellipse. The name of the use case is written inside
or underneath the ellipse. The participating actors are connected with the use
case by a solid line. Several actors being connected with a use case means that all
of them participate in that use case (AND semantics).
The use case buy soft drink in Figure 3.30 has exactly two actors: a customer
using the control panel to select a soft drink, and the card reader from which a
chip card is read and written for payment.
The system the use case refers to can be drawn as a box around the use case,
or use cases ( Figure 3.30 ). Having a system boundary is important for use case
modeling since it determines who the actors are and what execution steps the
use case describes.
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