1. A method for use in a video surveillance system in which at least a first set of trajectories of a first set of objects of a particular object class is hypothesized to have been moving through an area under surveillance at a previous point in time, the method comprising identifying objects of said particular class hypothesized to be in said area under surveillance at a current point in time, said particular class of objects being distinguishable from other objects based said particular class of objects' physical appearance, at least one of said objects in said area under surveillance at said current point in time being identified independent of the physical appearance of any objects hypothesized to have been in said area under surveillance at said previous point in time, and extending at least ones of said first set of trajectories to at least ones of said identified objects to develop at least one set of extended trajectories, each of at least ones of said extended trajectories being a respective one of said first set of trajectories extended to at least of the identified objects.