sentence: it defines : the coded representation of the spatio-temporal positioning of audio-visual objects as well as their behavior in response to interaction ( scene description ) ; the coded representation of synthetic two-dimensional ( 2d ) or three-dimensional ( 3d ) objects that can be manifested audibly and/or visually ; the extensible mpeg-4 textual ( xmt ) format - a textual representation of the multimedia content described in mpeg-4 using the extensible markup language ( xml ) ; and a system level description of an application engine ( format , delivery , lifecycle , and behavior of downloadable java byte code applications ) .