+The Tracker class uses the MTPGraph. From the definition of the
+spatial topology, it builds a graph with one source, one sink, and two
+nodes per location and time. This structure ensures the trajectories
+computed by the tracker to be node-disjoint by forcing the paths
+computed by the MTPGraph to be edge-disjoint.
+
+The edges from the source or to the sink, or between these pairs, are
+of length zero, and the edge between the two nodes of such a pair has
+a length equal to the opposite of the detection score.
+
+The file mtp.cc gives a very simple usage example of the Tracker
+class.
+
+The tracker data file one can read with Tracker::read has the
+following format (with L the number of locations and T the number of
+time steps):
+
+---------------------------- snip snip -------------------------------
+L T
+
+allowed_motion_from_1_to_1 ... allowed_motion_from_1_to_L
+...
+allowed_motion_from_L_to_1 ... allowed_motion_from_L_to_L
+
+is_an_entrance_1 ... is_an_entrance_L
+
+is_an_exit_1 ... is_an_exit_L
+
+detection_score_1_1 ... detection_score_1_L
+...
+detection_score_T_1 ... detection_score_T_L
+---------------------------- snip snip -------------------------------
+
+--
+François Fleuret
+August 2012