8. A computer implemented system for authoring a presentation of temporal media and nontemporal media, comprising: a timeline comprising one or more tracks enabling a user to specify a sequence of temporal media and enabling a user to specify nontemporal media in a temporal relationship with the temporal media; data defining a spatial relationship among the temporal media and the nontemporal media in a display area including an indication for each track in the timeline and for the nontemporal media a portion of the display area in which temporal media from the track will be displayed and a portion of the display area in which nontemporal media will be displayed; an interface enabling the user to modify the data defining the spatial relationship by wherein the graphical user interface also enables the user to modify the data defining the spatial relationship by presenting to the user, for each portion of the display area, the tracks available for the portion of the display area, and receiving from the user an indication of a track selected by the user for each portion of the display area; and one or more outputs through which the temporal media are presented, and in which at least the nontemporal media are presented in the specified spatial relationship with the temporal media and with the temporal relationship with the temporal media as specified by the timeline, for each of one or more specified times along the timeline.
9. The system of claim 8 , further comprising a time bar associated with the timeline and manipulable by a user to specify the one or more specified times.