Cheminformatics toolkits such as RDKit, ChemAxon, or Ambit enumerate all possible tautomers and generate a "canonical tautomer" for a compound by scoring all tautomers according to their respective rule sets. It has to be clear that, if these rule-based approaches could be compared with accurate experimentation and/or quantum chemical computations, the best that can be achieved would be "correctness" within the limit of statistical accuracy .