The graph 𝐺 ' !,# is converted to the simplified molecular-input line-entry system (SMILES) string of molecule 𝑞 ",$ for all analogue reactions 𝑗 ∈ 𝐽 under the level of all detected similar compounds 𝑠 " ∈ 𝑆. Each predicted molecule 𝑞 ",$ and each predicted reaction "𝑞 ",$ ↔ 𝑡" (in the form of one-to-one wiring), are compared with recorded molecules and reactions in the database respectively, by their canonical SMILES strings. If the reactions are unique, they are added into the predicted database to diversify the metabolic reaction space.