Pemodelan Perangkat Lunak

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Pemodelan Perangkat Lunak

• Sequence Diagram

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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

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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

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Elemen Notasi

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

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Elemen Notasi (cont.)

• A sequence diagram that has incoming and outgoing
  messages

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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

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Types of Interaction

• Creation
• Menunjukkan pesan yang menyebabkan terjadinya
  pembentukan instan obyek.
• Synchronous
• Pesan yang dikirim oleh 1 obyek ke obyek lain dan
  obyek pertama menunggu sampai hasil aksi selesai.
  
• Asynchronous
• 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
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Guidelines for Building a UML Sequence Diagram

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

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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

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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.

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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.

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Message (cont.)

• the system object calling its determineAvailableRe
  ports method.

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Message (cont.)

• Asynchronous Messages digunakan pada proses
  konkurensi

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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

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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.

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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.
• if I buy three items, then I get 20 off my
  purchase else I get 10 off my purchase.

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Alternatives (cont.)
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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).

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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.
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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.

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Loops (cont.)
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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.

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Interaction Occurrence
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Interaction Occurrence (cont.)
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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

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Gates (cont.)
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Gates (cont.)
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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

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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.

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Parallel (cont.)
A microwave is an example of an object that does
two tasks in parallel
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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.

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References

• UML 2.0 Superstructure Final Adopted
  Specification
• UML 2 Sequence Diagram Overview
• UML 2 Tutorial

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Try this yourself

• Draw up a sequence diagram modelling the case
  when an advert campaign manager retrieves the
  details of a particular clients 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

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A Solution to Previous Slide
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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 co-ordinates. 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.

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A Solution to Previous Slide
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Question