An approach to

Identifying the objects and classes

• place the candidate objects into two categories
  • objects that are the primary abstractions of the problem domain
  • objects that support the implementation
    

Defining the interface

• identify the behaviors

• assign the responsibilities

• leads to operations that will be used to manipulate the objects we've identified
  

Questions to consider for each operation

• How specific is the operation?
  • Is it common to an entire class hierarchy?
  • Or is it specific to a subtype?
    
• Is the operation common across several types?
  • If so, is it a candidate for a template function?
    
• Is the operation type-dependent?
  
  
• What is the visibility of the operation?
  • Should it be available to the entire program? (Þ public visibility)
  • Should it be restricted to the class hierarchy? (Þ protected visibility)

Describing the process control

The structure tree