“…They rely on Conditional Random Fields [17,27], belief Propagation [29,9], Dynamic or Linear Programming [3,10]. Among the latter, some operate on graphs whose nodes can either be all the spatial locations of potential people presence [26,11,5,1], only those where a detector has fired [25,15], or short temporal sequences of consecutive detections that are very likely to correspond to the same person [21,30,23,4].…”