ACL-IJCNLP 2021 The 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing Proceedings of the Conference, Vol. 1 (Long Papers) August 1 - 6, 2021 Diamond Sponsors Platinum Sponsors Gold Sponsors ii Silver Sponsors Bronze Sponsors ©2021 The Association for Computational Linguistics Order copies of this and other ACL proceedings from: Association for Computational Linguistics (ACL) 209 N. Eighth Street Stroudsburg, PA 18360 USA Tel: +1-570-476-8006 Fax: +1-570-476-0860
[email protected] ISBN 978-1-954085-52-7 (Volume 1) iii Message from the General Chair I am delighted to welcome you to the Joint Conference of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (ACL-IJCNLP 2021)! We are very grateful for many people. Fei Xia, Wenjie Li (Maggie) and Roberto Navigli, as the Program Chairs, have admirably guided the work of main conference organization and management. The calm and experienced Priscilla Rasmussen has done a lot of work for the signing of contracts with virtual platform company, Underline.io, calculation of registration fees and managing the entire registration process, and communication with sponsors and exhibitors. The amazing 68-person organizing committee, who all contributed so much to make the conference successful: Local Chairs (Priscilla Rasmussen, Thepchai Supnithi, Thanaruk Theeramunkong), Tutorial Chairs (David Chiang, Min Zhang), Workshop Chairs (Kentaro Inui, Michael Strube), Student Research Workshop Chairs (Jad Kabbara, Haitao Lin, Amandalynne Paullada, Jannis Vamvas), Faculty Advisors to the Student Workshop (Jing Jiang, Rico Sennrich, Derek F.