This is a UML class diagram example for the Command design pattern.
Purpose
Encapsulates a request allowing it to be treated as an object. This allows the request to be handled in traditionally object based relationships such as queuing and callbacks.
Use When
You need callback functionality.
Requests need to be handled at variant times or in variant orders.
A history of requests is needed.
The invoker should be decoupled from the object handling the invocation.
