Let's recall that a candidate is defined as a triplet of edges, which is used to create a new representation for the graph as explained in Figure . The topological genome is chosen as the lexicographically smallest key extracted from the candidates, so the set of candidates must be chosen in a fashion that is independent of the initial representation of the graph, lest the selection biases the search space. As a consequence, Delgado-Friedrichs and O'Keeffe proposed the following selection pattern: