TY - CONF A1 - Nakov, Preslav A1 - Da San Martino, Giovanni A1 - Elsayed, Tamer A1 - Barrón-Cedeño, Alberto A1 - Míguez, Rúben A1 - Shaar, Shaden A1 - Alam, Firoj A1 - Haouari, Fatima A1 - Hasanain, Maram A1 - Babulkov, Nikolay A1 - Nikolov, Alex A1 - Shahi, Gautam Kishore A1 - Struß, Julia Maria A1 - Mandl, Thomas T1 - The CLEF-2021 CheckThat! Lab on Detecting Check-Worthy Claims, Previously Fact-Checked Claims, and Fake News T2 - Advances in Information Retrieval N2 - We describe the fourth edition of the CheckThat! Lab, part of the 2021 Cross-Language Evaluation Forum (CLEF). The lab evaluates technology supporting various tasks related to factuality, and it is offered in Arabic, Bulgarian, English, and Spanish. Task 1 asks to predict which tweets in a Twitter stream are worth fact-checking (focusing on COVID-19). Task 2 asks to determine whether a claim in a tweet can be verified using a set of previously fact-checked claims. Task 3 asks to predict the veracity of a target news article and its topical domain. The evaluation is carried out using mean average precision or precision at rank k for the ranking tasks, and F1 for the classification tasks. KW - Fake news KW - Fact-checking KW - Falschmeldung KW - Desinformation KW - Fehlinformation Y1 - 2022 UR - https://opus4.kobv.de/opus4-fhpotsdam/frontdoor/index/index/docId/2607 SN - 978-3-030-72240-1 SP - 639 EP - 649 PB - Springer CY - Cham ER -