Some chemical structures can be drawn as different graphical representations, e.g. when the chemical structure can exist in multiple tautomeric and/or resonance forms. In most cases, preferred representations can be identified and these have been used to derive structure drawing conventions that should be used when processing chemical structures in Nexus to produce optimum results. Using the structure Drawing Conventions (available from the 'Related documents' below) ensures consistency with the training sets used in Nexus, e.g. for Sarah, Derek negative predictions and EC3 predictions. Using alternative structure representations may produce different results, and Lhasa is currently working to add functionality within Sarah Nexus to convert these alternatives to their preferred forms prior to processing.