In the process of developing procedures for TDT3, some changes were made to the TDT2 annotation guidelines. One of the most significant changes has been a shift in the classification of a "story" for segmentation and annotation purposes.
For TDT2, a quantity-based story definition was employed: a "story" was "a section containing at least two independent declarative clauses on the same topic." For TDT3 purposes, this definition has been modified to encourage a more content-driven deliniation of what constitutes a story.
In order to capture those stories (reports) which may be of a very limited length, a distinction was established between "preview" and "news report" sections of a broadcast. "Previews" consist of short teasers which are designed to capture the viewer/listener's attention. These "previews" are promotional spots for stories which will be reported on more fully later in the broadcast. "News reports" are contentful stories which provide information about a topic. "News reports" may be any length, even fewer than two independent declarative clauses, but they are complete reports on a story rather than promos for upcoming segments.
In TDT3, "previews" are classified as non-news during the segmentation process, while "news reports" are preserved for later annotation.