Com S 362 Lecture Outline
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            INTERACTION DIAGRAMS IN UML

- In previous lectures, we studied the static 
  relationships in the system. However, dynamic 
  interaction is also important. Interaction diagrams 
  provide a detailed representation of the steps of 
  interaction between entities in a software system 
  that is necessary to fulfill some goal.

- key idea: show how entities in the same interact
  with each other to fulfill the overall responsibility
  of the system

- a number of different types of interaction diagrams 

  > sequence diagram: useful for high-level scenario
       often useful for emphasizing the order of events
       in the system.
  > communication diagram: useful for showing connections
       between entities. 
  > timing diagram: useful for showing timing constraints
       between events in the system. Not a UML invention, 
       has been around for ages in the electrical engg.
       community.
  > interaction overview diagram: a combination of activity
       diagram and sequence diagram

- Each has unique characteristics
  
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                  NOTATIONS

Things to watch out for:

  instances are underlined
                start with a colon

    |-----------|
    | :PMSD     | (should be underlined)
    |-----------|

  classes are not underlined, no colon

    |-----------|
    | Math      | (not underlined)
    |-----------|

  multiobjects (collections)
      have double boxes

      |-----------|
    |-----------| |
    |  :File    |-| (should be underlined)
    |-----------|

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   EXAMPLE COMMUNICATION DIAGRAM 

       |
       | makePayment(cashTendered)
       | |
       | v
       |
   |-----------|
   | :Register |
   |-----------|
       |
       | 1: makePayment(cashTendered)
       | |
       | v
       |
   |-----------|
   | :Sale     |
   |-----------|
       |
       |
       | 1.1: create(cashTendered)
       |  |
       |  v
       |
   |------------|
   |  :Payment  |
   |------------|

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         SEQUENCE DIAGRAM

Example sequence diagram for line and containing
points, which shows the sequence of calls/messages
events exchanged between entities of the system.

       |------|        |------------|       |------------|
       |:Line |        | start:Point|       |  end:Point |
       |------|        |------------|       |------------|
          |                  |                    |
moveBy    |                  |                    |
========>| |    moveBy       |                    |
         | |===============>| |                   |
         | |                | |                   |
         | |                | |                   |
         | |                 |      moveBy        |
         | |====================================>| |
         | |                 |                   | |
         | |                 |                   | |
         | |                 |                    |
         | |                 |                    |
          |                  |                    |