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So what happens here is a synchronization of the fl ows. In our case, we have to
synchronize the independent fl ows before they reach the last action??” confi rm
usage start . Otherwise, the faster fl ow part would trigger the confi rmation before
the other fl ow part has been fully traversed ( Figure 2.56 ).
2.4 Modeling Use Cases
90 CHAPTER 2 The Pragmatic SYSMOD Approach
Altogether, we obtain the result shown in Figure 2.56 for the use case start car
usage . This result shows the standard fl ow without exceptions or variants, based
on the essential steps.
Unfortunately, we have introduced some redundancy in our model. First, we
denoted the essential steps textually near the use case. Second, exactly these steps
are also described as actions in the activity diagram. If you were to change something
in the essential steps as you progress, it would very likely lead to inconsistencies due
to redundancy. It could easily happen that you change the textual description, but
overlook the corresponding actions in the activity, or vice-versa.


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