Content definition language

A content definition language is a specialized scripting language which advanced source ports use to define additional custom content.

Examples include:
 * DDF (standing for Doom Definition File), used by EDGE
 * DED (standing for Doomsday Engine Definitions), used by Doomsday and Risen3D
 * DECORATE, used by ZDoom, GZDoom, Skulltag and Vavoom
 * EDF (standing for Eternity Definition File), used by Eternity Engine
 * RMOD (standing for ReMooD Map Object Data), used by ReMooD

The difference with other scripting languages such as ACS or FraggleScript is that they cannot be used to alter a level directly, but are instead used to create new actors such as obstacles, monsters, weapons or items that can be placed on a map.