“…In general, supervised approaches consider relation extraction (RE) as a multi-class classification problem where each class corresponds to a predefined relation type (Zhang et al, 2017;Wu, 2019). In addition to the set of positive relations (henceforth PR) which corresponds to the taxonomy of relations of interest (like hypernymy, meronymy, and cause-effect relationships), most popular datasets manually annotated either for generic (e.g., SemEval-2010 Task 8 (Hendrickx et al, 2010), TACRED (Zhang et al, 2017)) or domain specific relations (e.g., ChemProt (Krallinger et al, 2017), BizRel (Khaldi et al, 2021)) include a negative relation (henceforth NR) to account either for the absence of a relation between two target entities (see NO-RELATION in TACRED), or any other types of relations not present in the annotation scheme (see OTHERS in SemEval-2010 and BizRel). NRs share two main characteristics: (C1) they have irregular and unstable linguistic realizations and (C2) are often over-represented making PR hard to predict due to the highly imbalanced nature of the problem (see the ratio of NR in Table 1).…”