15. The computer program product of claim 14 , wherein the layout specification is further defined by a document in a markup language that defines a set of frames in a display area, and wherein a definition of each frame in the set of frames includes an indication of a track of the timeline or nontemporal media to which the frame is assigned.
15. The computer program product of claim 14 , wherein the layout specification is further defined by a document in a markup language that defines a set of frames in a display area, and wherein a definition of each frame in the set of frames includes an indication of a track of the timeline or nontemporal media to which the frame is assigned. 16. The computer program product of claim 15 , wherein the document in the markup language further includes additional nontemporal media that is displayed as part of the presentation.