UML Weekend Crash Course™ - To Parent Directory

Session 17—Applying the Sequence Diagram to the Case Study 183
The system uses this item number to ask Inventory if the product is available in step 10.
Inventory replies that it is available (true) in step 11. Since the product is available, the
system tells the Order to mark the item “filled”, in step 12, and to return the actual Product
in step 13. The system uses the Product to tell Inventory to remove this Product from the
Inventory records because it has been allocated to the Order. The Inventory responds saying
that the operation succeeded (return true in step 15).
: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
6: getItem():int
7: return item #1
8: getProdSerialNbr(itemnbr:int):int
9: return prodserialnbr 27
10: [item found] getProduct(prodserialnbr:int):boolean
11: return true
12: [product found] fillitem(itemnbr:int):Product
13: return Product 123
14: reduceinv(prod:Product):boolean
15: return true
Figure 17-6 Complete the sequence of messages.
In Figure 17-6, you can also see the object activations, the narrow vertical rectangles on
the timelines. The object activations indicate when each object is busy. Typically the activation
begins when a message hits the timeline and ends when the response is sent back. In
the case of the system object, the activation runs the entire length showing that the system
is overseeing the entire set of interactions. This is sometimes referred to as the focus of
control.