From the standpoint of time, the smallest unit of a video is a single frame. Node segmentation could be performed at the frame level—a straightforward task as a frame is easily identifiable. However, a single frame cannot contain video information, since videos are necessarily dynamic. Analogously, a single word separated from a text does not convey meaning. Thus it is necessary to consider the scene, which is the next level of temporal organization. A scene can be defined as the minimum sequential set of frames that conveys meaning. This is an important concept for hypervideo, as one might wish a hypervideo link to be active throughout one scene, though not in the next. Scene granularity is therefore natural in the creation of hypervideo. Consequently, hypervideo requires algorithms capable of detecting scene transitions. One can imagine coarser levels of temporal organization: scenes can be grouped together to form a narrative sequence, which in turn are grouped to form a video. From the point of view of node segmentation, however, these concepts are not as critical.