Command

• Also known as: Action; Transaction
• Encapsulate a command request as an object
• Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations

Command

• Declares an interface for executing an operation

ConcreteCommand

• Defines a binding between a Receiver object and an action
• Implements Execute by invoking the corresponding operation(s) on Receiver

Client

• Creates a ConcreteCommand object and sets its receiver

Invoker

• Asks the command to carry out the request

Receiver

• Knows how to perform the operations associated with carrying out the request.