The success of databases is largely attributable to their ability to allow access to their content, based on the queries related to specific aspects of that content. On the World Wide Web also, search engines have played a major role in granting easier access to textual information. Currently, commercial tools to provide content-based access to visual information are in their early infancy. A video or a television event can be considered a vast stream of data representing intensity value at a point in an image. This intensity value represents some physical attributes in space for the scene captured by a camera.
Viewers are interested in objects, their characteristics, relationships and temporal history.
A video is interesting because it provides that information. We can also view a physical event as the evolution of spatio-temporal characteristics at a certain location. Now, as the amount of data increases, human ability to specify the location decreases. Thus, a system that will provide facilities to specify objects and events and will return or retrieve data corresponding to those will be much more interesting and useful to humans. At any given time, we can only see the world, or the environment, from one perspective.