The five basic procedures of the coordinator agent are (see fig.4): message acquisition, grouping measurements into trajectories (temporal integration), matching trajectories into top-level objects (spatial integration), formation of top-level trajectories, and observer coordination. These procedures transform the lower level structure components into the higher level ones, and their activation order depends on run-time detected conditions, such as the arrival of a new measurement, or when a certain observer looses the tracked object from its visual field. The required opportunistic activation can be adequately expressed within the blackboard [16,17] design pattern, which is often used in the distributed solving of the complex problems. The main subjects in such organization are knowledge sources (the basic procedures), the central data structure or blackboard (common view of the scene) and the control component which triggers the activation of knowledge sources (see fig.5).
