Latent Separation Boundary. With the verifications above and the previous work of analyzing the latent space of generative models , we assume that there exists a separation boundary which separates groups of molecules for each molecular property (e.g., drug-like and drug-unlike) and the normal vector of the separation boundary defines a latent direction which controls the degree of the property value (in Fig. ). When z moves toward and crosses the boundary, the molecular properties change accordingly (e.g., from drug-unlike to drug-like). A perfect separation boundary would have molecules with different properties well separated on different sides. From that, we can find a separation boundary for each molecular property with a unit normal vector n ∈ R l , such that the distance from any sample z to the separation boundary as: