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SEQUENCE DIAGRAM
E. Haodudin Nurkifli
Teknik Informatika
Universitas Ahmad Dahlan
Pertemuan : 6

SEQUENCE DIAGRAM
Merupakan suatu diagram interaksi yang
memodelkan suatu skenario tunggal yang dijalankan
pada sistem
 Digunakan untuk memperlihatkan interaksi antar
obyek dalam perintah yang berurut.
 Tujuan utama adalah mendefinisikan urutan
kejadian yang dapat menghasilkan output yang
diinginkan


SEQUENCE DIAGRAM
Partisipan : obyek atau entitas yang bertindak dalam
sequence diagram
 Message : komunikasi antar obyek partisipan
 Terdapat 2 tipe garis yaitu vertikal dan horisontal


 Vertikal

: waktu  maju berdasarkan waktu
 Horisontal : obyek mana yang beraksi

ELEMEN NOTASI
Didefinisikan pada UML 2.0
 Digambarkan dalam bentuk frame
 Bersifat optional untuk menggambarkan batas grafis
suatu diagram.


ELEMEN NOTASI (CONT.)



A sequence diagram that has incoming and outgoing
messages

ELEMEN NOTASI (LABELING)
DiagramType
DiagramName


The UML specification provides specific text values
for diagram types
 sd

= Sequence Diagram,
 activity = Activity Diagram,
 use case = Use Case Diagram

TYPES OF INTERACTION


Creation
●



Synchronous
●



Pesan yang dikirim oleh 1 obyek ke obyek lain dan obyek pertama
menunggu sampai hasil aksi selesai.

Asynchronous
●



Menunjukkan pesan yang menyebabkan terjadinya pembentukan
instan obyek.

Pesan yang dikirim oleh 1 obyek ke obyek lain dan obyek pertama
tidak menunggu sampai hasil aksi selesai.

Reply
●

Menunjukkan nilai kembali dari obyek ke obyek yang megirim
pesan

Sumber : schaum outline

GUIDELINES FOR BUILDING A
UML SEQUENCE DIAGRAM
1.
2.
3.
4.
5.

6.

Set the context (i.e. scope the system)
Identify participating objects
Draw arbitrary lifelines for each class
Draw the duration of the objects on the class lifeline
Insert the object messages from top to bottom of
diagram (time-based)
Check the diagram for completeness

LIFELINES
Elemen notasi lifeline terletak pada posisi atas
diagram
 Represent either roles or object instances that
participate in the sequence being modeled
 Standar penamaan lifeline :


 Instance

Name : Class Name

MESSAGES
The first message of a sequence diagram always starts
at the top and is typically located on the left side of
the diagram for readability.
 Subsequent messages are then added to the diagram
slightly lower then the previous message.


MESSAGE (CONT.)







the analyst object makes a call to the system object which is an instance of the
ReportingSystem class.
The analyst object is calling the system object's getAvailableReports method.
The system object then calls the getSecurityClearance method with the argument of
userId on the secSystem object, which is of the class type SecuritySystem
the secSystem object returns userClearance to the system object when the
getSecurityClearance method is called.
The system object returns availableReports when the getAvailableReports method is
called.

MESSAGE (CONT.)



the system object calling its
determineAvailableReports method.

MESSAGE (CONT.)



Asynchronous Messages : digunakan pada proses
konkurensi

GUARDS


When modeling object interactions, there will be times when a
condition must be met for a message to be sent to the object.



the guard is the text "[pastDueBalance = 0]." By having
the guard on this message, the addStudent message will
only be sent if the accounts receivable system returns a
past due balance of zero

COMBINED FRAGMENTS (ALTERNATIVES,
OPTIONS, AND LOOPS)
A combined fragment is used to group sets of
messages together to show conditional flow in a
sequence diagram.
 The UML 2 specification identifies 11 interaction
types for combined fragments.


ALTERNATIVES
Alternatives are used to designate a mutually
exclusive choice between two or more message
sequences.
 Alternatives allow the modeling of the classic "if then
else" logic e.g.


I buy three items, then I get 20% off my purchase; else I
get 10% off my purchase.

 if

OPTION
The option combination fragment is used to model a
sequence that, given a certain condition, will occur;
otherwise, the sequence does not occur.
 An option is used to model a simple "if then"
statement (i.e., if there are fewer than five donuts on
the shelf, then make two dozen more donuts).


OPTION (CONT.)

if a student's past due balance equals zero, then the addStudent,
getCostOfClass, and chargeForClass messages are sent. If the student's
past due balance does not equal zero, then the sequence skips sending any
of the messages in the option combination fragment.

LOOPS
Occasionally you will need to model a repetitive
sequence.
 In UML 2, modeling a repeating sequence has been
improved with the addition of the loop combination
fragment.


REFERENCING ANOTHER SEQUENCE
DIAGRAM
Starting in UML 2, the "Interaction Occurrence"
element was introduced.
 Interaction occurrences add the ability to compose
primitive sequence diagrams into complex sequence
diagrams.
 The text "ref" is placed inside the frame's namebox,
and the name of the sequence diagram being
referenced is placed inside the frame's content area
along with any parameters to the sequence diagram.


INTERACTION OCCURRENCE (CONT.)

GATES
Gates can be an easy way to model the passing of
information between a sequence diagram and its
context.
 A gate is merely a message that is illustrated with one
end connected to the sequence diagram's frame's edge
and the other end connected to a lifeline


BREAK


almost identical in every way to the option combined
fragment, with two exceptions.






a break's frame has a namebox with the text "break" instead of
"option."
when a break combined fragment's message is to be executed, the
enclosing interaction's remainder messages will not be executed
because the sequence breaks out of the enclosing interaction

break combined fragment is much like the break keyword
in a programming language like C++ or Java
Breaks are most commonly used to model exception
handling

Pertemuan 6-2-sequence-diagram

PARALLEL








When the processing time required to complete portions of
a complex task is longer than desired, some systems handle
parts of the processing in parallel
The parallel combination fragment is drawn using a frame,
and you place the text "par" in the frame's namebox
break up the frame's content section into horizontal
operands separated by a dashed line.
Each operand in the frame represents a thread of execution
done in parallel.

PARALLEL (CONT.)

A microwave is an example of an
object that does two tasks in parallel

SUMMARY
The sequence diagram is a good diagram to use to
document a system's requirements and to flush out a
system's design.
 The reason the sequence diagram is so useful is
because it shows the interaction logic between the
objects in the system in the time order that the
interactions take place.


REFERENCES
UML 2.0 Superstructure Final Adopted Specification
 UML 2 Sequence Diagram Overview
 UML 2 Tutorial


TRY THIS YOURSELF…
Draw up a sequence diagram modelling
the case when an advert campaign
manager retrieves the details of a
particular client’s advertising campaign
and lists the details of a particular advert
from the campaign. The sequence diagram
should also show the case when a new
advert is created. Only call messages
(synchronous) should be used in this
example and use any iteration conditions
as you deem necessary.
Objects to use: “CampainManager”, “Client”,
“Campaign”, and “Advert”

A SOLUTION TO PREVIOUS SLIDE
:CampaignManager

:Client

:Campaign

:Advert

getClientName()

listCampaigns()
[For all client's campaigns]*getCampaignDetails()

listAdverts()
[For all adverts in campaign]*getAdvertDetails()

addNewAdvert()
Advert()
new Ad:Advert

TRY THIS TOO…
Create a sequence diagram modelling the behaviour of
a PCB drilling machine. The machine will drill holes
in a PCB of given dimensions at a set of given coordinates. Co-ordinates are given as a list, which must
contain at least one set of co-ordinates. Drilling stops
when the end of the list is reached or when a user
interrupts the process.

A SOLUTION TO PREVIOUS SLIDE
loadFile(file)
:Computer

:drillController

:Driller

Drill(coord)
initSeq()

move(offset)

finalSeq()

[while not EOF]*Drill(coord)

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Pertemuan 6-2-sequence-diagram

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