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The solid line between an actor and a use case is formally an association. It
means that the actor and the system communicate in the context of the use case.
A use case can also be abstract. It then represents common features with similar
use cases. Similar to an abstract class, the name is written in italics, and it can
be optionally completed by the adjective {abstract} . Concrete use cases are connected
with the abstract use case by a generalization. This is the same relationship
as between classes. Reading in the direction of the arrow, the sentence ??? use case A
is a kind of use case B ??? has to make sense. Otherwise, there is a modeling error.
3.5 The Use Case Diagram
FIGURE 3-30
A use case with actor and system.
uc Soft-drink vending machine
Customer
Card reader
?«system?»
Soft-drink vending machine
Buy soft drink
170 CHAPTER 3 UML??”Unifi ed Modeling Language
Let ??™ s test this on the example in Figure 3.31 :
?–  Delete soft-drink data is a kind of change soft-drink data .
?–  Modify soft-drink data is a kind of change soft-drink data .


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