This volume contains the proceedings of the Twenty-fourth European Conference on Artificial Intelligence (ECAI 2020), held from August 29th to September 8th, 2020, in Santiago de Compostela, Spain, though mainly online due to the COVID-19 situation that has hit the world. Since 1974, the biennial European Conference on Artificial Intelligence, organized by the European Association for Artificial Intelligence (EurAI), has been the premier venue for presenting AI research in Europe. ECAI is the place for researchers and practitioners of Artificial Intelligence (AI) to gather and to discuss the latest trends and challenges in all subfields of AI as well as to demonstrate innovative applications and uses of advanced AI technology.

ECAI 2020 had a record number of submissions with more than 1700 abstract submissions of which 1443 papers were reviewed; this represents a doubling of previous stand-alone ECAI conferences. Of these 1443 papers, 1363 were full papers and 80 2-page highlight papers. Finally, 362 full-papers and 36 highlight papers were accepted, yielding an acceptance rate of 25% for full-papers and 45% for highlight papers. The largest number of submissions where in the broad areas of Machine Learning (31%), Natural Language Processing (12%), Vision (9%), Knowledge Representation and Reasoning (9%), Multi-agent Systems (7%), and Explainable AI (4%). Most of the submissions came from Europe (41%, including Israel since it is part of EurAI, the European Artificial Intelligence Association), followed by Asia (33%), Americas (9%), Oceania (2%), and Africa (0.4%). Note that 14% of the papers had authors coming from different continents.

ECAI 2020 coordinated with AAAI 2020, IJCAI 2020, AAMAS 2020 and ICAPS 2020 for deadlines and synergies. In particular we had a special procedure to allow ECAI 2020 to transfer a paper on Planning and Scheduling to ICAPS 2020 (with the authors’ permission), and vice-versa. In the end no paper was transferred but having the transfer procedure available has been a plus, transforming competition into cooperation between the two conferences.

The program of ECAI 2020 included 5 keynote speakers, namely Luc De Raedt, Stuart J. Russell, Sylvie Thiébaux, Carme Torras, and Moshe Y. Vardi, and 4 additional invited speakers in the “Frontiers of Artificial Intelligence” track, namely Blai Bonet, Randy Goebel, Rada Mihalcea, and Magdalena Ortiz.

ECAI 2020 included 29 tutorials, selected by the Tutorial Chairs, Meghyn Bienvenu and Claudia d’Amato, and 31 associated workshops selected by Amparo Alonso-Betanzos and Magdalena Ortiz, who served as Workshop Chairs. Following tradition, ECAI 2020 incorporated the 10th Conference on Prestigious Applications of Intelligent Systems (PAIS 2020), chaired by Bistra Dilkina and Michela Milano. The 12 papers from PAIS are included in this volume.

ECAI 2020 had a special focus on starting researchers, who had the opportunity of participating in several specific events including the 9th Starting AI Researcher Symposium (STAIRS) chaired by Sebastian Rudolph and Goreti Marreiros, a Doctoral Consortium, with training and mentoring phases, chaired by Ulises Cortés and Jose Alonso in collaboration with STAIRS, the traditional Meeting with an EurAI Fellow, and a Job Fair. It also included a Women in AI Meeting chaired by Hanan Salam and Marwa Chafii of the international organization Women in AI.

I would like to thank the authors, the Area Chairs (ACs), Senior Program Committee members (SPCs), and regular Program Committee members (PCs), for their work, which unfortunately spanned over the December 2019 holidays. Ultimately the high quality of the papers included here depends on them all.

I also want to thank all chairs who have done an excellent job in their selection tasks and have been very prompt and active and responsive for the entire period of the conference organization.

I am particularly grateful to Jérôme Lang, the General Chair of ECAI 2020, who provided several important suggestions given his experience with IJCAI-ECAI 2018. He has really been my point of reference in taking all my decisions. I am obliged to Tito Cruz from confDNA who helped me in the assignment of the papers to ACs, SPCs, and PCs and then helped me again in organizing the papers for the ECAI 2020 technical sessions. Without his help I would have been lost. I am also obliged to Alejandro Catalá who helped me first in making the experience of handling a big conference such ECAI 2020 on EasyChair bearable, and then handled the management of the camera-ready versions of the papers and of the proceedings. Thank you, Alejandro. Many people helped me in my department at Sapienza, too many to list them all here, but I want to mention my student Manuel Namici and my postdoc Alessandro Ronca who helped me in analyzing the data coming from the conference by preparing a relational database with all the data and then providing me with excel files to play with to take my decisions.

I want to thank the previous ECAI program chairs and organizers for suggestions, in particular Torsten Schaub who shared all his notes from ECAI 2014 that have been tremendously helpful for starting up my own work. I also want to thank the many colleagues with whom I have discussed ECAI 2020 issues in these years, again they are too many to list, I mention only Diego Calvanese, Hector Geffner, Erez Karpas, Maurizio Lenzerini, Alessio Lomuscio, Yves Lesperance and Fabio Patrizi, whom I “tortured” quite regularly before taking decisions.

I want to close by mentioning that during the organization of ECAI 2020 the outbreak and the COVID-19 disease had a deep impact on the whole world. ECAI 2020 originally scheduled in Santiago de Compostela Spain in June 8–12, 2020 had to be moved to August 29–September 8, 2020 and done fully online.

Handling this situation has been extremely challenging and we formed a small action group to appropriately react to it. The group was formed by Senén Barro (Organizing Chair), Alberto Bugarín (Organizing Co-Chair), Jérôme Lang (General Chair), Barry O’Sullivan (EurAI President), and myself (Program Chair). Later we asked Carsten Lutz to join this group and capitalized on his experience in handling EDBT/ICDT 2020 online. This group has been very effective in taking all the decisions regarding how to transform the on-site conference to an online one.

We are all indebted to Senén and Alberto and the whole ECAI 2020 Local Organizing Team at CiTIUS and USC in Santiago de Compostela. The fantastic managerial capability of Senén, the meticulous organization of Alberto, and the hard work of all the people at CiTIUS and USC working with them, have made it possible to run ECAI 2020 smoothly in spite of all odds, while keeping it financially feasible. I want to thank our partners Underline.io, that handled the online streaming of the whole conference, also for them running such a large conference fully online for the first time has been a challenge, and Whova, that adapted with us its technology for navigating the conference program, something even more critical when the conference is fully online. Finally, I want to thank the sponsors for ECAI 2020, who did not abandon the conference once we decided to hold it online.

Giuseppe De Giacomo

Program Chair, ECAI 2020