UML Weekend Crash Course™ - To Parent Directory

Session 18—Modeling the Dynamic View: The Collaboration Diagram 191
7. Comment: Reference 7 shows one way that you can reveal your intention to repeat
a set of messages. As with Sequence diagrams, comments can be very helpful for
explaining your intentions regarding iteration across a set of messages because the
iteration notation provided by the UML works only for a single event.
Now I’ll change a few items on the diagram so that you can see some new notations. The
following descriptions refer to the numbered items in Figure 18-4.
9:
Bill:
Customer
1
1:Order()
3:addItem(characters)
10:cancel()
Bill’s Order :
Order
2:return Order
8:return
11:return
5:return product available
7:addProduct(characters)
2
4:productAvailable(characters)
6:[product available]
reduceInventory(product #, qty)
:Inventory
Figure 18-4 More Collaboration diagram notation
Note the following items on the diagram:
1. Timeout event: I haven’t labeled this message, mostly because a timeout would be
a bit unusual for this type of scenario. This way you get to see the notation anyway.
Actually, this is a common extension to the UML (that is, it isn’t explicitly
defined by the UML). The small circle represents a clock and sometimes even shows
the clock hands within the circle. A timeout would be used for something like
dialing into a network or polling a node on a network. If you don’t get a response
within a specified amount of time, you abandon the attempt and move on. In this
case, if the Order doesn’t respond within the specified time limit, the Order is cancelled
in step 10.
2. Asynchronous message: An asynchronous message does not require a reply. Step 6
has been altered to simply tell the Inventory, “I’ve taken some of your stock. You
might want to update your records. But I’m not going to wait around until you do.”