| ID | Definition |
---|---|---|
SMILES attribute | Sk | SMILES atom, i.e., one symbol (e.g. ‘C’, ‘N’, ‘=’, etc.) or a group of symbols that cannot be examined separately (e.g., ‘Cl’, ‘Br’, Si’, etc.) |
 | SSk | a mixture of two SMILES-atoms |
 | BOND | Presence or absence of chemical bonds: double (=), triple (#), and stereochemical (@) or @@) |
 | PAIR | Association two of BOND, NOSP, and HALO |
 | HARD | Association of BOND, NOSP, and HALO in the united structural code |
 | NOSP | Presence or absence of different chemical elements: nitrogen (N), oxygen (O), sulfur (S), and phosphorus (P); |
 | Cmax | Maximum number of rings |
 | Nmax | Maximum number of nitrogen atoms in a molecule |
 | Omax | Maximum number of oxygen atoms in a molecule structure |
Graph invariant | e2k | Morgan extended connectivity of first order |
 | e3k | Morgan extended connectivity of second-order |
 | pt2k | Number of paths of lengths 2 and 3 starting from a given vertex in the graph |
 | pt3k | Number of paths of length 3 starting from a given vertex in the graph |
 | S2k | Valence shells of the second orders |
 | S3k | Valence shells of the third orders |
 | C5 and C6 | Codes of rings (five-member and six-member rings, with the data on the presence or absence of heteroatoms, aromaticity, and the total number of given rings in the molecule) |