An other example is sr-tree [7], whose nodes are determined with the intersection of a ball and a rectangle. BAR-tree =-=[4]-=- is another tree based on the kd-tree with the relaxation of orthogonal splitting hyperplanes. In the other words, splitting hyperplanes can be non-orthogonal...
Consider a social group (for example, a political decision group). In this context, each vertex in the signed graph represents a person in this social group while an edge represents a sentiment relation (mutual liking or disliking, friendship or enmity, cooperation or defection, interaction or ...