Embedding means that the system will interact with many other (external) systems.
Consequently, many external systems are actors participating in the use cases. The
pertaining diagram has a Star pattern, which we already know from the system context
diagram ( Figure 2.41 ).
We are now ready to assign actors to the use cases identifi ed so far. We have
actually done some when we identifi ed the use cases. We try to fi nd the actors that
participate in each use case. Each actor also has to appear in the system context
model. Since we are now looking closer at the details of our system it is absolutely
normal to discover new actors. We extend the system context model accordingly.
FIGURE 2-40
An actor and a use case.
uc [package] SysML book [actor/use case]
Actor Use case
FIGURE 2-41
Actors and the use case ??? start car usage. ???
uc [package] Start car usage [actors]
Reservation
system
Start car
usage
Central locking system
Drive-away protection Customer
75 2.4 Modeling Use Cases
The dependency on the system context arises from the fact that we have
redundant information in the model.
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