VAST is designed for any on-demand video player where the ad response is parsed prior to play. For example, use of this standard would be appropriate within an Adobe Flash player if the ad response was requested and parsed in ActionScript but would not be appropriate if contained directly within a SMIL playlist directly sent to the player. It may be possible to use this XML format for applications other than on-demand viewing such as live video streaming, downloadable video players, set-top boxes, etc, but those applications are explicitly beyond the scope of the current effort.
The goal of this specification is to be compatible with any video player framework that has the ability to be scriptable. It will be up to each Secondary Ad Server to develop its own implementation of the standard and it will be up to each publisher or vendor to implement the standard in their Primary Ad Server and their Video Players.