Interaction modeling

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Interaction modeling

• Object Interaction is dynamic behaviour modeling
• It is used to show the interactions which occur
  between the static Class Diagram and the Use
  Cases
• This integration of the users view (Use Case
  model) and the developers view(Class Diagram) is
  used to cross check the requirements of the system

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Interaction modeling

• As we have seen and used.
• The Class Diagram for a problem defines the
  internal structure of the objects (by defining
  the class content) but does not show how the
  objects will interact
• Use Cases depict the processes without concern
  for the internal composition of the processes
• Interaction modeling increases the chances of the
  system achieving what the user wanted

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Interaction modeling

• Object interaction modeling involves two types of
  modeling diagram derived from Use Cases
• Object Sequence Diagram(OSDs)
• Object Collaboration Diagram(OCDS)
• Use the Together booklet to see how to draw them

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Sequence Diagram

• Illustrate how objects interact with each other
• Focus on message sequence

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Object Sequence Diagram

• The Object Sequence Diagram(OSD) represents a
  graphic description of a Use Case
• Constructs of sequence, selection and iteration
• passage of time also depicted on the diagram

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Hotel Example - Use-case view

• Hotel UCD

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Hotel Example - Use Cases

• Check_in use case
• This use case begins when a visitor enters the
  hotel.
• The system checks if the visitor had booked a
  room.
• If yes then the S1. If not the system checks if
  there are free rooms. If yes the room is reserved
  for the visitor and the S1. If not the case is
  finished with the message - NO Vacancies.
• S1. Room is allocated to the visitor. Message
  GIVE KEY is send to the receptionist. The visitor
  receives a VISITORS CARD.
• Check_out use case
• This use case begins when a visitor arrives at
  the reception desk in order to check out the
  hotel.
• The system calculates the bill. The visitor pays.
  The system sends a message to the cleaner to
  clean up the left room. COLLECT KEY is send to
  the receptionist. The visitor returns the key the
  visitors card.

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Hotel Example - Class Diagram
Hotel
available (r Room)
1
1
guests
Room
Cleaner


HotelGuest
size Number
pay Money
clean Bool
leave ()
clean (r Room)
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Hotel Example - Class diagram

• Persons involved

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Hotel Example - State Diagram

• Room class

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Hotel Example - Sequence Diagram
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Sequence Diagram

• Purpose
• capture the behaviour of a single use case -
  how messages are sent within a use case
• show how objects interact with each other - show
  how they send and receive messages
• focus on time

• Syntax
• object
• time
• message

• Forms
• generic - all possible alternative scenarios
• instance - one scenario, no conditions, branches,
  loops

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Sequence Diagram

• Example

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Messages

• Message
• a communication between objects that conveys
  information
• has a render and recipient
• is represented as an arrow denoting flow of
  control

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Sequence Diagram

• Types of messages
• simple
• flat flow of control - control is passed without
  describing any details
• synchronous
• nested flow of control - operation call
• handling of the message is completed before the
  caller resumes execution
• asynchronous
• there is no explicit return to the caller
• the sender continues to execute after sending the
  message without waiting for it to be handled

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Sequence Diagram

• Activation
• time during which object performs an action
  either directly or through another object
  (subcontractor)

• Return
• implicit
• explicit

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Sequence Diagram

• Conditional branch

• Loop

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Sequence Diagrams

• Textual notes

• Time constrains

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Sequence Diagram

• Conditional branch

• Loop

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Tutorial - To create OSDs

• Using the Video Shop scenario
• Choose a use case such as Borrow a book
• Create a New Sequence Diagram for this use case