PubChemRDF: towards the semantic annotation of PubChem compound and substance databases

With the goal of semantically describing information available in the PubChem archive, pre-existing ontological frameworks were used, rather than creating new ones. Semantic relationships between compounds and substances, chemical descriptors associated with compounds and substances, interrelationships between chemicals, as well as provenance and attribute metadata of substances are described. Graphical abstract:Schematic representation of the semantic links for PubChem compounds and substances.