Extended overview of ChEMU 2021: Reaction reference resolution and anaphora resolution in chemical patents

In this paper, we provide an overview of the Cheminformatics Elsevier Melbourne University (ChEMU) evaluation lab 2021, part of the Conference and Labs of the Evaluation Forum 2021 (CLEF 2021). The ChEMU evaluation lab focuses on information extraction over chemical reactions from patent texts. As the second instance of our ChEMU lab series, we build upon the ChEMU corpus developed for ChEMU 2020, extending it for two distinct tasks related to reference resolution in chemical patents. Task 1 - Chemical Reaction Reference Resolution - focuses on paragraph-level references and aims to identify the chemical reactions or general conditions specified in one reaction description referred to by another. Task 2 - Anaphora Resolution - focuses on expression-level references and aims to identify the reference relationships between expressions in chemical reaction descriptions. Herein, we describe the resources created for these tasks and the evaluation methodology adopted. We also provide a brief summary of the results obtained in this lab, finding that one submission achieves substantially better results than our baseline models.