A few years ago, we published an article which drew a formal analogy between chemistry and iTunes (sic )[cite]10.1021/ci060139e[/cite]. iTunes was the first really large commercial digital music library, and a feature under-the-skin was the use of meta-data to aid discoverability of any of the 10 million (26M in 2013) or so individual items in the store. ^‡ The analogy to digital chemistry and discoverability of