OO Design

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OO Design

• Roshan Chitrakar

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Design Class Diagrams (DCD)

• DCD provides details of the software classes
  along with methods.
• DCDs are created in parallel with interaction
  diagrams or after them in rare cases.
• In practice, the creating the DCD begins with
  drawing a little of Interaction diagram and
  making DCDs. Then update Interaction diagram and
  then update DCDs.

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DCD Example
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Creating DCDs

• Identify software classes
• Illustrate them by Class Diagrams
• Add Method names
• Add Type information
• Add Association and Navigability
• Add Dependency relationship

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Identify Software Classes and Illustrate them by
Class diagrams

• Scan interaction diagrams and list all the
  classes
• Some of the domain classes may be absent here
• Some may appear later in the elaboration phase or
  when a new requirement is added

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Add Method Names
Go through the interaction diagrams and make a
list of all the messages.
Generally, messages coming to a class become
methods of the class.
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Method Name Issues

• The message create
• Accessing Methods
• Multi-objects
• Language dependent syntax

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Add Type Information

• Types of attributes, Parameters of methods and
  Return values are specified

Note All information must be added exhaustively
if CASE tools will be used for code generation.
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Add Associations and Navigability

• A role should be given uni-directional capability
  to navigate from source to target objects of
  classes.
• Navigability usually implies the attribute
  visibility. (shown by a line and an arrow)
• Navigability can also be identified from
  Interaction diagrams
• (p294, Larman)
• (p293, Larman)

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Association and Navigation
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Navigability from Interaction Diagram
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Add Dependency

• Dependency is illustrated with dashed arrow line
  (UML notation)
• It depicts non-attribute visibility (e.g.
  parameter, local, global visibility) also.
• So, it is recommended when local, parameter or
  global visibility exist among classes.

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Dependency