UML Weekend Crash Course™ - To Parent Directory

172
Saturday Afternoon
Bill : Customer
Bill's Order : Order
: Inventory
1
1: Order()
2: return order
3 *[for each product] : additem(product,qty)
4: addProduct(product,qty)
3
5: productAvailable(product,qty)
4
6: return yes
7: reduceInventory(product,qty)
8: return done
5
2
9: return done
10: cancel()
Figure 16-3 Extended elements of the Sequence diagram notation
Observe these notations in Figure 16-3:
1. Activation: The start of the vertical rectangle, the activation bar
2. Deactivation: The end of the vertical rectangle, the activation bar
3. Timeout event: Typically signified by a full arrowhead with a small clock face
or circle on the line
4. Asynchronous event: Typically signified by a stick arrowhead
5. Object termination symbolized by an X
X
Figure 16-3 also introduces some new types of messages. Reference #3 points to a message
with a circle on the line and the stereotype . This is called a timed event.
Often there is also a condition or a constraint on the message that expresses the timing
parameters for the event, for example, {if we don’t get a response from inventory within
2 seconds we will bypass the item and check later}. The timeout is an example of a UML
extension. It is not a part of the core UML notation, but represents a valid usage.