This design pattern decouples an abstraction from its implementation so that the two can vary independently.

The classes and objects participating in this pattern include:

• Abstraction (BusinessObject)

  • defines the abstraction's interface.
  • maintains a reference to an object of type Implementor.

• RefinedAbstraction (CustomersBusinessObject)

  • extends the interface defined by Abstraction.

• Implementor (DataObject)

  • defines the interface for implementation classes. This interface doesn't have to correspond exactly to Abstraction's interface; in fact the two interfaces can be quite different. Typically the Implementation interface provides only primitive operations, and Abstraction defines higher-level operations based on these primitives.

• ConcreteImplementor (CustomersDataObject)

  • implements the Implementor interface and defines its concrete implementation.