UML Weekend Crash Course™ - To Parent Directory

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Saturday Evening
The next step is “getOrder” from the database. In the flowchart, I stated that this was a
call to the Find Order Use Case. In order to keep the focus on the Sequence diagram construction,
I model it here as a procedure call with a response. In Figure 17-4, steps 3 and 4 show
the call and response.
:OrderFulfillment Clerk :System :OrdersDB 12345678:Order 23456789:Order :Inventory
1: getOrderNbr():int
2: return12345678
3: getOrder(ordernbr:int):Order
4: return Order 12345678
Figure 17-4 Add steps 3 and 4; get the Order using the order number
The return is simply the data (the Order) being sent back as a result of performing the
operation. Remember that the Sequence diagram is modeling a test case, so the return should
be a value. Sometimes you’ll model a rule, in which case you would show the return data type
rather than a specific value.
The next step is “display Order.” Because this message does not require a response,
Figure 17-5 shows the use of an asynchronous communication using a line-style arrow.
There is no corresponding return arrow.
:OrderFulfillment Clerk :System :OrdersDB 12345678:Order 23456789:Order :Inventory
1: getOrderNbr():int
2: return 12345678
3: getOrder(ordernbr:int):Order
4: return Order 12345678
5: displayOrder(Order):void
Figure 17-5 Add an asynchronous message.
The rest of the steps are modeled in Figure 17-6. After the Order is displayed in step 5,
the system asks the user for the first item to look up (step 6, getItem():int). The system is
expecting to get an integer representing the number of the item on the Order to look up. It
gets the reply “item #1” in step 7. The system uses the item number in step 8 to ask the
Order for the corresponding product serial number. The Order returns the product serial
number in step 9.