EVENT REPORT

Report on the 30th The Web Conference 2021
(TheWebConf2021)
Aljaž Košmerlj
Artificial Intelligence LaboratoryJožef Stefan Institutealjaz.kosmerlj@ijs.si

Marko Grobelnik
Artificial Intelligence LaboratoryJožef Stefan Institutemarko.grobelnik@ijs.si

Jure Leskovec
Computer Science Department
Stanford University
jure@cs.stanford.edu
Abstract
The Web Conference (TheWebConf2021) is the premier conputer science conference on thestate of the Web and its related areas. It covers the Web from a wide spectrum of aspects,
including technical areas of artificial intelligence, security, privacy, knowledge representation,
mobile computing as well as social sciences, economics, policy, accessibility and others. Theyear 2021 marked the 30th edition that was organised in Ljubljana, Slovenia, but took place
fully online due to the COVID-19 pandemic.

1Introduction

The Web Conference is focused on understanding the current state and the evolution of the Web
through the lens of computer science, computational social science, economics, policy, and manyother disciplines. The year 2021 marks the 30th edition of the conference which was to take placein Ljubljana, Slovenia. Unfortunately, due to the COVID-19 pandemic, the conference had to bemoved online.
The main conference took place from April 19th to 23rd and was preceded by a whole weekof workshops and tutorials from April 12th to 16th. Additionaly, this year was the first time a
pre-conference event with five keynote talks was organised before the conference on April 1st andwas open for free attendance.

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The conference organising committee consisted of:General Chairs:• Jure Leskovec, Stanford University• Marko Grobelnik, Jožef Stefan InstituteDevelopers Track Chairs:• Andreas Harth, University of ErlangenNuremberg• Dan Brickley, Google

Program Committee:• Leila Zia, Wikimedia Foundation• Jie Tang, Tsinghua University• Marc Najork, Google

Diversity & Inclusion Chair:• MunMun De Choudhury, Georgia Tech
PhD Symposium Chairs:• Gregoris Mentzas, National Technical University of Athens• Dunja Mladenić, Jožef Stefan Institute• Rudi Studer, Karlsruhe Institute of Technology

Local Organizing Committee:• Aljaž Košmerlj, Jožef Stefan Institute• Marija Komatar, Pitea
Local Volunteers Chair:• Lovro Šubelj, University of Ljubljana

Student Scholarship Chairs:• Srijan Kumar, GaTech• Shobeir Fakhraei, Amazon• Ben Steichen, Cal Poly Pomona

Tutorials Track Chairs (hands-on):• Bob West, EPFL
• Marinka Žitnik, Harvard
Tutorials Track Chairs (lecture):• Smriti Bhagat, Facebook• Paul Groth, University of Amsterdam

2Workshop Track Chairs:• Julian McAuley, UC San Diego• Karthik Subbian, Amazon

Sponsorship & Networking Chairs:• Mark Minevich, Going Global Ventures• Balaji Krishnapuram, Pinterest• Yang Yang, Zhejiang University• James Shanahan, UC Berkeley

Demos Track Chairs:• James Hodson, AI for good• Janez Brank, Jožef Stefan InstituteCommunications & Social Media Chairs:• Peng Zhang, Zhipu.AI• Rayid Ghani, Carnegie Mellon University

Panels Chairs:• Ricardo Baeza Yates, NTENT & Northeastern University• Emine Yilmaz, University College London

Proceedings Chairs:• Luca Aiello, Nokia Bell labs
• Meeyoung Cha, KAISTPapers

For its main research paper track The Web Conference seeks submissions that describe in-depth
studies to improve our understanding of the Web and its impact, introduce technical and sociotechnical advances that enhance and expand Web platforms and technologies, and make strides
in democratizing access to Web information and knowledge.

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In the 2021 conference the specific topics of interest were highlighted in 12 research tracks listed
in Table 1 along with the number of accepted submissions per track. Each paper was limited tomaximum 12 pages and if accepted had a 15-minute presentation.
Track Name
Crowdsourcing and Human Computation
Economics and Monetization
SearchSecurity, Privacy, and Trust
Semantics and Knowledge
Social Network Analysis and Graph Algorithms
Systems and Infrastructure
User experience and Accessibility
User Modeling and Personalization
Web and Society
Web Mining and Content Analysis
Web of Things, Ubiquitous, and Mobile Computing

Nr. of Submissions
4368120152
144
305
5414259
161
288
93

Table 1: TheWebConf2021 research tracks and their respective numbers of submitted papers.
In total, the program committee (PC) received 1,736 submissions of which 355 (20.5%) wereaccepted. The papers review process was coordinated and performed by 3 PC heads, 28 track
chairs, 171 senior PC members, 1000 PC members and 743 additional reviewers.
Proceedings The conference proceedings have been published by ACM. Their release has
been delayed due to additional organisational strain because of the COVID-19 pandemic and thepublication was finalized in early June 2021. The proceedings are split into the main volume[pro, 2021], containing the word from the organisers and the papers from the main track, and thecompanion proceedings [com, 2021], containing the contributions from workshops, tutorials andother tracks.

3

Tutorials and Workshops

A broad program of tutorials and workshops was a priority for the organising committee and awhole week before the main conference (April 12-16) was dedicated to them. A special emphasis
was given on making a portion of the tutorials hands-on, with the attendees actively participating
and gaining practical experience. Overall, there were 23 tutorials (Table 2) and 25 workshops(Table 3)1 .

1

For full descriptions and authors see: https://www2021.thewebconf.org/program/workshops/ and https://www2021.thewebconf.org/program/tutorials/

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Tutorial Title
SWApi: SPARQL Endpoints and Web APIInformation extraction from social media: A hands-on tutorial on tasks, data, & open source
tools
Neural Structured Learning: Training Neural Networks with Structured Signals
Recommender Systems through the Lens of Decision Theory
Building an Efficient Text Classifier from the Ground Up
Introduction to Deep Learning with PyTorch
Deep Recommender System: Fundamentals and Advances
Scaling out NLP Applications to 100+ Languages
Learning from Comparisons
Bias Issues and Solutions in Recommender System
Uplift Modeling: from Causal Inference to Personalization
Advanced Deep Graph Learning: Deeper, Faster, Robuster, Unsupervised
Graph Mining and Multi-Relational Learning: Tools and Applications
Going for Speed: Full-Stack Performance Engineering in Modern Web-Based Applications
Responsible AI in Industry: Practical Challenges and Lessons Learned
Exploring Biomedical Web Resources Using Shell Scripting
Large Scale Graph Mining: Visualization, Exploration, and Analysis
PyNetworkshop: Analyzing the Structure of Networks in Python - The Essentials, Signed
Networks, and Network Optimization
Improving Web Ranking with Human-in-the-Loop: Methodology, Scalability, Evaluation
Flatland: Multi-Agent Reinforcement Learning on Trains
Conversational Artificial Intelligence: Can Your AI Beat the Turing Test?
Machine Learning-Driven Ad Blocking: From Data Collection to Deployment
Learning from Graphs: From Mathematical Principles to Practical Tools

Table 2: The list of tutorials.

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Workshop Title
11th Temporal Web Analytics Workshop (TempWeb)
7th WebAndTheCity – Web Intelligence and Resilience in Smart Cities
Third Workshop on Fairness, Accountability, Transparency, Ethics and Society on the Web(FATES 2021)
CLEOPATRA’2021: The 2nd International Workshop on Cross-lingual Event-centric OpenAnalytics
Data-efficient Machine Learning for Web Applications (DeMaL)
1st International Workshop on Scientific Knowledge Representation, Discovery, and Assessment(Sci-K)The 1st International Workshop on Deep Learning for the Web of Things
First International Workshop on the Efficiency of Modern Datacenters (EMDC)
The 9th International Workshop on Natural Language Processing for Social Media (SocialNLP2021)
2nd Workshop on Deep Reinforcement Learning for Knowledge Discovery
The International Workshop on Semantics-enabled Biomedical Literature Analytics (SeBiLAn)
8th Wiki Workshop
The First Workshop on Financial Technology on the Web
Beyond Facts: 1st International Workshop on Knowledge Graphs for Online Discourse Analysis
Workshop Data Science for Social GoodFirst International Workshop on News Recommendation and Intelligence
NLP Beyond Text - 2nd Edition Workshop Proposal
Workshop on Misinformation Integrity in Social Networks
LocWeb 2021 at The Web Conference 2021
Workshop on Multilingual SearchInternational Workshop on AI in Health: Transferring and Integrating Knowledge for Better
HealthKMEcommerce: Knowledge Management in E-Commerce Workshop 2020
Workshop Proposal: Graph Learning Benchmarks (GLB 2021)
The International Workshop on Self-Supervised Learning for the Web (S2L@WWW 2021)
The 3rd Innovation Workshop on Transforming Big Data into Actionable Knowledge (BiDAW)

Table 3: The list of workshops.

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4Special Tracks and Panels

The conference hosted three special tracks covering specialized topics:
Web of Health: Organised by Tim Althoff (University of Washington) and Emre Kiciman(Microsoft Research), it covered topics in health and medicine which are increasingly searched
for and tracked online, and their relevant content is often delivered via digital means. The track
explored new opportunities to improve our health and the delivery of medicine and strengthen theconnection between healthcare and web research communities.
Future of the Web: Organised by Evgeniy Gabrilovich (Google), this track hosted a series of
keynote talks regarding the trends and technologies that will mark the future development of theweb. It explored both the look forward with respect to the technical and conceptual progress of
the web as well as the societal impacts of web technologies.
Web4All: Organised by Silvia Rodrı́guez (University of Geneva) and Ted Drake (Intuit), thisspecial track deals with all aspects of web accessibility. Exploring factors such as health, disability,culture, age, income, language and many others. This edition focused on the impacts of extreme
events, such as the recent COVID-19, which can drastically change the way we interact with eachother and with everything that surrounds us and web technology can play a crucial role in suchcircumstances.
The conference also hosted two panels:
Ethics & Fairness on the Web: Moderated by Ricardo Baeza-Yates (Institute for ExperientialAI, Northeastern University) and including:• Jeanna Matthews - Professor, Department of Computer Science, Clarkson University• Gregor Strojin - Chair of Ad Hoc Committee on Artificial Intelligence at Council of Europe• Nisha Talagala - CEO and Founder at AIClub World
Conversational Systems on the Web: Moderated by Emine Yilmaz (University CollegeLondon & Amazon) and including:• Eugene Agichtein - Professor, Emory University and Amazon Scholar, Amazon• Julia Kiseleva - Senior Researcher, Microsoft• Mark Sanderson - Professor, RMIT University• Idan Szpektor - Staff Research Scientist and Manager, Google

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5Keynotes

The conference held a broad program of keynotes starting with the pre-conference event on April
1st, 2021, which served as a warm-up for the main conference. The pre-conference talks were:• Evelyne Viegas (Microsoft Research): Challenges in Machine Learning – Designing highimpact competitions for the benefit of society• Denny Vrandečić (Wikimedia Foundation): Towards knowledge equity: A world where everyone can share in the sum of all knowledge• Marko Grobelnik (Jožef Stefan Institute): Cross-lingual Global Media Monitoring• Stan Matwin (Dalhousie University): Artificial Intelligence for People Emotion Detection
During COVID-19 Social Isolation• Jure Leskovec (Stanford University): Mobility network models of COVID-19 explain inequities and inform reopening
During the main conference the keynotes (split between morning and afternoon sessions were):• Verica Trstenjak (University of Ljubljana & SFU Vienna): Human rights in the Digital Era• Fausto Giunchiglia (University of Trento): Diversity, Bias, Online Social Relations andRelated Issues• Anju Kambadur (Bloomberg LP): Knowledge Graphs & Natural Language in Finance• Lada Adamic (Facebook): The Geography of Social Ties
• Yejin Choi (University of Washington): Commonsense Intelligence: Cracking the Longstanding Challenge in AI• Estevam Hruschka (Megagon Labs): Implications and Explanations in User-Generated Data
• Elena Simperl (King’s College London): The Web of Data: How are we Doing so Far?
• Krysta Svore (Microsoft Research): Enabling the Quantum Revolution — Pioneering Advances to Achieve Quantum Computing and Impact at Scale• Ganesh Mani (Carnegie Mellon): AI Grand Challenges: Past, Present and Future (SeeKeynote section of this journal issue)

6Awards

The program committee selected the best paper and the best student paper amongst all the published submissions. The selection process was led by the best paper award chairs, Kira Radinsky(Technion & Diagnostic Robotics) and Ahmed H. Awadallah (Microsoft Research), and chose thefollowing papers:
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• Best Paper Award: Towards Facilitating Empathic Conversations in Online Mental
Health Support: A Reinforcement Learning Approach [Sharma et al., 2021], by authors:
Ashish Sharma, Inna Lin, Adam Miner, David Atkins and Tim Althoff.
• Best Student Paper Award: ConceptGuide: Supporting Online Video Learning withConcept Map-based Recommendation of Learning Path [Tang et al., 2021], by authors:
Chien-Lin Tang, Jingxian Liao, Hao-Chuan Wang, Ching-Ying Sung and Wen-Chieh Lin.
In the scope of The Web Conference IW3C2 also awards the Seoul Test of Time Award.
This year, the 7th award was given to a paper from the 2011 edition of the conference titled:
Information Credibility on Twitter [Castillo et al., 2011], by authors: Carlos Castillo, Marcelo
Mendoza and Barbara Poblete.
The organising committee takes this opportunity to congratulate all the authors of the winning
papers again on their excellent work.

7Organisation

The conference took place fully online due to the restrictions and circumstances arising fromthe COVID-19 pandemic. The MiTeam platform2 was used for all the sessions including thetutorials, workshops and panels. Selected keynotes were also streamed publicly via Youtube. All
the conference activity was recorded totalling at over 550 hours of program. The recodings will
be made available on the Videolectures.net platform3 except in rare cases where author consent
was not given.
Over all the events the conference was attended by 2,843 participants (this includes the free
pre-conference event) with over 2,400 more viewing the public Youtube streams. There were 918
registered participants from 62 countries of which 37% were students. With the kind support ofour sponsors, especially Web4Good and NSF, we were able to cover registration costs with student
scholarships for 188 students.
The conference would not be possible without the kind support of our sponsors: Microsoftresearch, Huavei, Amazon Science, Facebook, Pinterest, Finvolution, Megagon Labs, Google,
Bloomberg Yahoo Research, Pošta Slovenije, Qlector, EventRegistry, NSF, The Web Conference,and Outbrain. Key support was also extended by our participating instututions: IW3C2, Jožef
Stefan Institute, Stanford University, IRCAI, and Videolectures.net.
Lastly, the conference chairs would like to thank the local and global community as well as
our families and friends for all the support given during organisation. Though your contributions
may not be explicitly mentioned in the document, we could not have done it without you.

23

https://miteam.eu/
http://videolectures.net/www2021_Ljubljana/

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References
WWW ’21: Companion Proceedings of the Web Conference 2021, New York, NY, USA, 2021.
Association for Computing Machinery. ISBN 9781450383134.
WWW ’21: Proceedings of the Web Conference 2021, New York, NY, USA, 2021. Association for
Computing Machinery. ISBN 9781450383127.
Carlos Castillo, Marcelo Mendoza, and Barbara Poblete. Information credibility on twitter. InProceedings of the 20th International Conference on World Wide Web, WWW ’11, page 675–684,
New York, USA, 2011. ACM. ISBN 9781450306324. doi: 10.1145/1963405.1963500. URL
https://doi.org/10.1145/1963405.1963500.
Ashish Sharma, Inna W. Lin, Adam S. Miner, David C. Atkins, and Tim Althoff. Towards
facilitating empathic conversations in online mental health support: A reinforcement learningapproach. In Proceedings of the Web Conference 2021, WWW ’21, page 194–205, New York,NY, USA, 2021. Association for Computing Machinery. ISBN 9781450383127. doi: 10.1145/3442381.3450097. URL https://doi.org/10.1145/3442381.3450097.
Chien-Lin Tang, Jingxian Liao, Hao-Chuan Wang, Ching-Ying Sung, and Wen-Chieh Lin. Conceptguide: Supporting online video learning with concept map-based recommendation of learning path. In Proceedings of the Web Conference 2021, WWW ’21, page 2757–2768, NewYork, NY, USA, 2021. Association for Computing Machinery. ISBN 9781450383127. doi:
10.1145/3442381.3449808. URL https://doi.org/10.1145/3442381.3449808.

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