1. A method for describing adaptive mobile multimedia applications or presentations, whose playback behavior depends on a current quality of service (QoS) during playback, in an XML-based document that is interpreted by an entity playing back multimedia content, the method comprising: describing, in the document, intrinsic adaptation possibilities of application or presentations, which run in a mobile network environment, in an Adaptation Module including a programming language structure required for describing the adaptation possibilities of said adaptive mobile applications; playing back an initial continuous media item during the current QoS; specifying, in the document, alternative media items to be reproduced when a change in the current QoS during playback prevents the initial continuous media from being played back, said alternative media items being specified with a choose element having a startmode attribute which specifies a playtime at which reproduction is started for a continuous media item of the alternative media items after an adaption to the change in the current QoS; and after adaption to the change in the current QoS, playing back the continuous media item of the alternative media items according to the startmode attribute instead of the initial continuous media item.