A complex problem arises in connection with enhanced video: where a trigger comes through while an enhancement is already being displayed, how should that trigger (and its associated enhancement) be handled?
This problem could arise, for instance, where a show is enhanced, and an embedded ad is also enhanced; a show is enhanced in two places, and a viewer is still in the first enhancement when the second trigger arrives; two ads are enhanced, and a viewer is still in the first ad's enhancements when the second trigger arrives.
Conventionally, when one encodes triggers, client systems—for instance set-top boxes manufactured under license from WEBTV Networks, or Liberate Technologies—provide no effective control of overlapping enhancements. Some conventional client systems completely ignore the second trigger; this is undesirable for the sponsor of the second trigger as well as the programmer who sold that trigger spot. In other conventional client systems, if the new trigger does not contain the same URL as the currently displayed screen (which is not necessarily the URL in the old trigger), the new trigger pops up and the viewer has 10 seconds to choose the new trigger over the old enhancement. While this approach may better accommodate sponsors, it is inflexibly disruptive to the viewers. Still further, it also has problems where copies of the same trigger can disrupt subsequent screens of the first trigger's enhancements.
It would be desirable for a solution to exist which allowed for flexible control of overlapping enhancements. Still further it would be desirable for such a solution to be able to flexibly allow for overlapping enhancement control to be varied based on broadcast context. For instance, it would be desirable for a solution to exist for different broadcasters to specify how overlapping enhancements would be handled, and a similar pair of overlapping enhancements handled in accordance with the broadcasters' specifications.