SEQUENCE DIAGRAMS
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Transcript SEQUENCE DIAGRAMS
Ana M. Fernández
[email protected]
A UML diagram that depicts:
◦ interactions between objects.
◦ how the business currently works by showing how
various business objects interact.
Purpose:
1. Model flow of control
2. Identify synchronization
3. Illustrate typical scenarios
The focus is less on messages themselves and
more on the order in which messages occur.
The diagram conveys this information along 2
dimensions:
◦ the vertical dimension shows, top down, the time
sequence of messages/calls as they occur,
◦ the horizontal dimension shows, left to right, the object
instances that the messages are sent to.
Instance Name : Class Name
◦ Underlined specific instance (Bill, Fred)
◦ Not underlined kind of instance or role (buyer,
seller)
Message =a line to the receiving object with:
◦ a solid arrowhead (if a synchronous call operation)
◦ a stick arrowhead (if an asynchronous signal)
The message/method name is placed above the
arrowed line.
Return message = dotted line with an open arrowhead
back to the originating lifeline (above the return value
from the operation).
To model mutually exclusive choice between two
or more message sequences (if then else)
The word "alt" is placed inside the frame's
namebox.
Operands are separated by a dashed line.
To model a
sequence that,
given a certain
condition, will
occur; otherwise,
the sequence does
not occur (If then).
The word “opt" is
placed inside the
frame's namebox.
To model a repetitive sequence.
The word “loop" is placed inside the frame's
namebox (add the minimum and maximum of
iterations)
To model parallel
processing
activities.
The word “par" is
placed inside the
frame's namebox.
Break up the
frame horizontal
operands
separated by a
dashed line.
Messages:
◦ Synchronous
◦ Asynchronous
◦ Return
Alternative
Option
Loop
Pararell