
Modeling Solutions ◾ 173
e auction activity diagram contains three instances of repetition.
One loop describes the user advancing from one item to the next and ter-
minates when there are no more items or when the user is nished view-
ing auction items. A second loop surrounds the rst loop, allowing the
user to place a bid before viewing the next item. e bottom loop allows
a user to nd out whether someone has placed a higher bid by refreshing
the current item.
6.4 CONTROL ABSTRACTION IN ACTIVITY DIAGRAMS
Activities do not need to be atomic actions. More complex activities can
be abstracted as a rectangle. Zooming in on the rectangle ...