Unique Identifiers for Chemicals

• Registry number
  • Assigned by an authority, Applies to any substance, Semantically void, Usually copyrighted and may require payment
  • Examples: CAS, RTECS

• Graph canonicalisation
  • Unique atom labelling assigned algorithmically
  • "Layers" manage differences between, Hydrogens and tautomerism, Stereochemistry, Isotopes
  • Semantically rich
  • IUPAC/NIST is Open and OpenSource, assimilated into CML

Example of INChI v0.932Beta
C7H6O2,1H3-5-4H-6(8)2H-3H-7(5)9