Figure 6

Generic compact representation of a neighborhood. Instead of explicitly storing all the set compositions as illustrated in figure 1b, only the size of the set corresponding to a node is stored. Nodes corresponding to singletons sets (leaf nodes) are labeled with the element of the set. The set corresponding to a particular node can be generated on the fly by searching the leaf nodes reachable from this set. During the bottom-up search of pertinent target sets, elements in common with the query set Q = {b, g} are propagated. i₁..i₇ correspond to iterations of the main loop (order in which the nodes are processed).