Name:
  Bridge

Intent:
  - avoid compile-time binding of an abstraction and its implementation
  - decouple an abstraction and its implementation so that the can vary independently

Structure:
  - abstraction holds a reference to its implementation
  - some operation of the abstraction are delegated to the implementation

Notes:
  - sometimes there are many implementation (and several abstractions)
  - sometimes applied to hierarchies
  - bridge capabilities are provided by delegation, not inheritance
  - see Proxy, Adapter, Facade