Fig. 1

a Valclavam is annotated in the PubChem (CID 126919) and ChEBI (CHEBI:9920) databases. b In PubChem, it is incorrectly assigned the class of beta-lactams, which are sulfur compounds. Moreover, although the latter can be either inorganic or organic, it is wrong to describe a single compound both as organic and inorganic. The transitivity of the is_a relationship is not fulfilled, which makes the class inference difficult. In ChEBI, the same compound is correctly classified as a peptide. However, as in PubChem, the annotation is incomplete. Class assignments to “clavams” and “azetidines”, among others, are missing