Facade

• A single class that represents an entire subsystem
• Provide a unified interface to a set of interfaces in a subsystem
• Define a higher-level interface that makes the subsystem easier to use

Facade

• Knows which subsystem classes are responsible for a request.
• Delegates client requests to appropriate subsystem objects.

Subsystem classes

• Implement subsystem functionality.
• Handle work assigned by the Facade object.
• Have no knowledge of the facade and keep no reference to it.