As mentioned in Introduction, the interactive compounds tend to participate in the same metabolic pathways. Accordingly, for a query compound, the higher interaction confidence score with its interactive compound, the more likely they are to participate in the same metabolic pathway. The more its interactive compounds involving in a certain metabolic pathway, the more likely it is to participate in such metabolic pathway. Based on these points, we should count not only the number of compounds interacting with the query compound, but also the corresponding interaction scores. Thus, the desired predictor can be formulated via the following procedures.