Module 4

Sequence Diagrams

Example Code and its sequence diagram

Public class A
{
    Private BB myB = new BB();
    Public void doOne()
    {
        myB.doTwo();
        myB.doThree();
    }
}

Sequence diagram for payment system

Sequence vs Communication

• UML tools usually emphasize sequence
• Easier to see call flow sequence—read from top to bottom
• Communication diagrams are more space-efficient
• Communication Diagrams expand top to bottom; Sequence Diagrams expand left to right

Common Notation

Singleton Objects

• Only one instance of the class instantiated at any time
  

Lifeline Boxes

• Lifeline is a dashed line below the object that creates a shortlived object
  

Messages

Reply or Returns

• Use the message syntax returnVar=Message(parameter)
• Using a reply or return message at the end of an activation bar
  

Messages to self

• We use a nested activation bar to satisfy this
  

Condition and looping

Other frame operators

Relating interaction diagrams

• Interaction occurances is a reference to an interaction within another interaction
  

Polymorphic Messages

Communication Diagrams

• Connection path between objects. Navigation and visibility. Instance of an association.
• Multiple messages and messages both ways
  

Creation of instances

Sequencing

Conditional Messages

Mutually Exclusive Conditions

Iterations

Design Class Diagrams

• During analysis emphasize domain concepts
• During design shift to software artifacts
• UML has no explicit notation for DCDs
• Uniform UML notation supports smoother development from analysis to design

Domain model vs design class diagram

Developing DCD for POS DCD

Adding dependencies:

An instance of product description is used by a method in the sale class making sale dependent on the product description.:

Composition (Whole part) relationship

an aggregation is shown with a hollow diamond instead of a fully coloured one.

Association Classes

Interfaces and template classes

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