More specifically, based on the graph representation of the chemical structures of all vertices of degree one. The concept of core scaffolds and analog series is also illustrated in Figure and discussed in detail elsewhere. Briefly, core scaffolds and analog series apply a series of fragmentation rules based on retrosynthetic feasibility. Two molecules are considered analogs if the fragmentation rules can map them to the same core fragment, and that fragment is a significant part of the molecule (usually, it contains at least two-thirds of the total number of heavy atoms of each molecule).