Sequence diagram in UML
Martin Palkovik
Sequence diagram
It is a graphic representation of system operations based on chronology - a time sequence
It represents the life cycle of the object for a period of time
Sequence diagram is part of the object - oriented model It is a dynamic view showing symbols of objects
(instances of classes) and messages between them Shows the interaction as two-dimensional graph The vertical axis represents time, the horizontal axis
shows the objects, which cooperate among themselves
Sequence diagram
Represents the behavior of objects in terms of interactions
Complement class diagram, which represents the static structure of the system
Sequence diagram for the designer is important because it clarifies the role of objects in time sequence, based on events
Sequence diagram units
Actor - characterized by an external user who is interacting with the system
In the sequence diagram has the actor lifeline, representing the length of his life
It is not possible to separate the actor and his lifeline If the user causes interaction, is often represented as the
most left or most right object in the sequence diagram, because he is external to the system
Sequence diagram units
Object - an instance of class
In sequence diagram object has lifeline(Dashed vertical line under the symbol object)
Time progresses downward line Lifeline object represents a period during which the
object exists. It is not possible to separate the object and lifeline. If the object is created and abolished in the same time
period depicted in the diagram, the lifeline begins and ends on the corresponding point.
Sequence diagram units
Message - the communication between objects
The report contains: Sender, recipient and action Sender is an object or actor, that send the message Recipient of an object or an actor, who receives the report Action is triggered to transfer information The message is displayed as a full horizontal arrow from lifeline of
one object or actor to lifeline of another object or actor. The arrow is named as the message title.
Sequence diagram units
Message shares the same concept in Collaboration in the Sequence diagram
It`s able to transfer between different types of diagrams When composing a message, we can also choose to
create an element activation, to show the process flow
Activation represents the period during which an object performs an activity
Exists only as a graphic symbol It is a thin rectangle, its upper edge is associated with initialization, the
bottom edge of the end
Recursive message message, sent by the
object itself The sender and receiver
are the same object
Recursive message with activation
If we want to do as easily readable diagram we draw the Return arrow, which displays the time, when the action returned to the sender
It is clear to return, resulting in a return value for the source
Links:
http://www.developer.com/article.php/3080941 http://stargate.cnl.tuke.sk/~ywetka/
DiagramInterakcie.pdf http://sk.wikipedia.org/wiki/Sekvenčný_diagram
Thank you