FIGURE 3-72
Example for a synchronous message.
sd Check PIN entered
:On-board computer
control
checkUsageRight()
:ReservationSystem
sd Identify customer
:Card reader
identifyCustomer(card data)
:On-board computer
control
Defi nition
A combined fragment describes an expression, consisting of an interaction
operator and interaction fragments as operands.
A sequence diagram represents a concrete scenario (i.e., an interaction between
selected elements in a limited situation). This is the reason why loops and
208 CHAPTER 3 UML??”Unifi ed Modeling Language
conditional branches are not needed as intensively as they are in activity diagrams,
which describe sets of possible flows. But they are helpful in modeling simple
variants of a flow.
The interaction operators of a combined fragment trigger the conditional execution
of an operand, loops, parallel execution, and other variants. The operands
are interaction fragments (i.e., a set of messages between lifelines).
A combined fragment is denoted similar to a diagram frame: a rectangle with
solid lines and a small pentagon in the upper left corner.
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