UML Weekend Crash Course™ - To Parent Directory

160
Saturday Afternoon
Figure 15-1 implies that you would let them try again or cancel. To do that, you need to
loop back to the beginning and offer them a choice. Figure 15-2 illustrates the needed
changes. To loop back to a previous place in the logic, use a merge point diamond. To provide
a choice, use the decision diamond. Then each path out of the decision diamond must
be labeled with a guard condition. In this case, you offer them two choices: proceed to
Enter Shipper_ID or cancel.
start
merge point
proceed or cancel
[cancel]
[proceed]
cancelled
Enter Shipper_ID
Prompt to
re-enter or
cancel
[Shipper not found]
Find Shipper
Display
Shipper details
[Shipper found]
Figure 15-2 Modeling a looping condition and merge point
Next identify the post-conditions and terminations. (I do these together because there is
often a great deal of overlap.) The narrative told you that the Use Case terminates when:
The system displays the message that it could not find the Shipping company and
the user cancels
Accounts Payable has been notified and the inventory has been updated
The user cancels the transaction