The graphic on the bottom depicts the stream of data as a sequence of stories and non-stories. Segmentation systems place boundaries between these units and the evaluation software measures the system's ability to do so.

Story segmentation performance depends on the form of the source and on the maximum time allowed before segmentation decisions must be output. These factors are taken into account for the evaluation by defining appropriate experimental control conditions.

For more information concerning the current research in TDT segmentation, there were two system description papers submitted for the 1999 TDT workshop. Also, the TDT Research Links contains pointers to previous year's TDT segmentation research.