The interrelationships within the set of connectivity-permuted species generated by the formalism can be represented as graphs. The component species are represented as "nodes" or graph vertices. The pairwise relationships between these are represented as graph edges connecting the graph vertices; each edge represents a R de c process equivalent to the elementary reaction. The entire graph represents the full network of desmotropic processes and hence a full network of reactions. A powerful corollary of this is that, at least where steric interactions allow, such a graph maps onto its corresponding potential energy surface (PES). These reaction graphs encode the "shape" (topology) of the corresponding chemical space. The unsymmetrical dissociation of the bifluoride anion (2a) into [HF + fluoride] (1a and 1b) is depicted in Fig. . This reaction is equivalently represented as the graph in Fig. where the graph vertices are labelled by their species. The 1D PES for the reaction with locations of the species indicated is shown in Fig. . While 2a has a well-defined position on the PES, species 1a and 1b are each located at an arbitrary point where one of the H-F connections of 2a is said to be qualitatively broken.