 Non-document sources. While this article has to be restricted to documents it should also be noted that an increasing amount of drug discovery data is beginning to surface on the web that may never be instantiated in document form. Although this started with PubChem Bioassay as far back as 2004, the more recent proliferation is via Open-notebook science. More projects are using open Electronic Laboratory Notebooks (ELNs) that are not only accessible to anyone by web browsing, but also, crucially, crawled by Google and indexed for chemistry searching  Structures: A necessary focus of this article will be traditional small-molecule chemistry that is not too far outside the Rule-of-Five lead-like property space. In terms of connectivity value antibodies, other protein biotherapeutics, as well as large peptides or polynucleotides, are also important to encompass. However, capture into structured records is more challenging for these larger modalities than for smallmolecules that can be merged on the basis of chemistry rules. Notwithstanding, space limitations mean that non-small molecule connectivity is out of scope for this article.