UML Weekend Crash Course™ - To Parent Directory

184
Saturday Evening
For Scenario 2, shown in Figure 17-7, insert a comment referring to steps 1 through 4 of
Scenario 1, and then add the new message for Scenario 2. The comment simply helps you
avoid having to repeat all the steps you’ve already documented in the previous Sequence diagram.
The comment is just a timesaving technique, not a part of the UML or any methodology.
The new message in this case is conditional. The condition “order not found” is placed in
square brackets [] before the message description. This indicates that the message will only
take place if the order is not found in a previous step.
:OrderFulfillment Clerk :System :OrdersDB 12345678:Order 23456789:Order :Inventory
Repeat steps 1 through 4 of Scenario 1, then
1: displayMsg(chars):void
Figure 17-7 Scenario 2
For Scenario 3, shown in Figure 17-8, again insert a comment for the repeated steps,
1 through 9 of Scenario 1. The only difference for this scenario is that it loops back to a
previous step. There is no additional processing. If I really fleshed this out I might add the
exception handling for items not found. For this course I simply indicate that the process
loops back to the test to see if the user is “Done” or there are “no unfilled items”
:OrderFulfillment Clerk :System :OrdersDB 12345678:Order 23456789:Order :Inventory
Repeat steps 1 through 9 of Scenario 1, then
If [item not found] return to the test "Done or no unfilled items"
Figure 17-8 Scenario 3
For Scenario 4, in Figure 17-9, continue from step 13 of Scenario 1. This time, the
process makes it all the way to the end but there are still unfilled items on the Order.
The system tells the Order object to create a backorder in step 1. The Order creates
another Order, passing itself as the reference so the backorder can track where it came from
(step 2). Note that the minus sign on the operation means that the operation is private
(that is, only objects of the same class may invoke it). Step 3 shows that the backorder was
successfully created. Step 4 shows the Order telling the System that it finished the task
requested in step 1.