RapidApplicationDevelopment (RAD) is the process of creating an application from a prototype (e.g., AppKit & Foundation), modifying as needed, instead of writing new code. A true RAD workflow includes a GUI design tool (InterfaceBuilder).

NeXTComputer shook the computing world with the introduction of RAD in the early 90’s, and continues to innovate with Cocoa.

See the Wikipedia entry for more details:

http://en.wikipedia.org/wiki/Rapid_Application_Development