text: LaSSI is similar to LSA in that it involves the construction of an occurrence matrix from a corpus of items and the application of singular value decomposition to that matrix to derive latent features.  What differs is that the occurrence matrix represents the frequency of two- and three-dimensional chemical descriptors (rather than natural language terms) found within a chemical database of chemical structures.  This process derives latent chemical structure concepts that can be used to calculate chemical similarities and structure–activity relationships for drug discovery.