Conference Warm-up & Reflecting on the Making of #RecSys2021

5 min readSep 23, 2021


Dear RecSys colleagues,

RecSys 2021 is just around the corner. Our organizing team is proud to be offering a hybrid conference with both in-person participants in Amsterdam, as well as online participants around the world. To get you warmed up for the conference, we wish to highlight a number of special aspects of the program and to exclusively show you a little bit of “The making of ACM RecSys 2021”.

Main Conference
Our main conference takes place 27 September — 1 October in the historic Amsterdam Stock Exchange Building, which has been transformed into the Amsterdam Conference Centre. From there, we will stream all presentations live around the world. As announced earlier, this week offers 3 keynotes, 49 technical papers, 3 reproducibility papers, 14 industry talks, 11 industry posters, 10 demonstrations, 23 late-breaking results, 8 doctoral symposium presentations, and 6 tutorials. RecSys2021 also offers 5 workshops and the RecSys Challenge. Finally, there are ample opportunities throughout the week to interact with our conference sponsors, both at the venue and via virtual sponsor events online. At the time of writing, we have topped 900 registrations for the conference and are heading for 1000. Of these, around 250 people will be attending the conference in-person in Amsterdam.

Photo by Agustin Diaz Gargiulo on Unsplash

ACM RecSys Goes Hybrid
We are proud that ACM RecSys 2021 breaks new ground by being one of the very first hybrid ACM conferences. We have introduced two key innovations that are designed to provide everyone with the best possible hybrid experience.

First, we have added a virtual “prelude & postlude” to the conference. Specifically, before and after the main week of the conference, we are offering virtual-only events that are attended by both online and in-person participants. The “prelude” starts with the Virtual Kickoff on Friday 24 September, which provides a “sneak peek” into the content of the conference, and brings people together to network and socialize. Both the “prelude” and “postlude” offer virtual workshops that are scheduled during the “Golden hours”, i.e., times at which most people in the world are awake and can come together simultaneously.

The complete program of the conference including virtual “prelude & postlude” is here:

Second, we have designed a special conference platform, called the virtual Hub. It provides a handy digital program and also (for online conference attendees) access to the live streams. A special feature of the Hub, which is particularly important for virtual participants, is the Hub Library. In the Library, there is a dedicated page for every conference paper. This page provides paper information and a link to the paper PDF on ACM Digital Library and “trailer” videos for poster presentations. Importantly, each paper page also provides two features that are particularly useful in a hybrid conference setting: Asynchronous Q&A, which allows participants to leave a question for the paper authors at any time during the conference, and catch-up videos, which allows participants to watch videos of talks during the main conference week that they might have missed. The virtual Hub will be available for 60 days after the conference finishes.In short, the Library means that you don’t miss out on conference content or interaction if you miss a session.

Photo by Rohan Rangaswami on Unsplash

Impact of covid-19
If “The making of ACM RecSys 2021” were a superhero movie, the global pandemic would be the supervillian. Covid-19 was definitely the main challenge that we faced and needed to overcome. There were two low points in our epic struggle. First, on 26 June this year, the Netherlands opened prematurely (e.g., its night clubs) causing a temporary covid-19 spike the week after our registration page went live. The second struggle came at the end of August, when the covid-19 cases surged in the US and the European Union imposed bans and required quarantines for overseas travelers. We keenly felt the disappointment among those of you who needed to cancel their in-person plans. We also felt your frustration two weeks later, when the quarantine requirement was lifted again.

As we look at the final program for the conference, we are happy with the extent to which we managed to outwit the supervillain. In the end, workshop organizers who could not travel to Amsterdam shifted the main focus of their workshop to the virtual “prelude & postlude” and away from the main conference week. Note that we needed to make sure that virtual-only offerings did not compete with offerings at the venue, in order to minimize the moments that in-person participants at the venue need to follow conference content online. We would say that this shift has been the main impact that the covid-19 low points have had on the conference program. We are, however, very pleased that no workshops needed to be cancelled. We are grateful for the dedication and flexibility of the workshop organizers.

Photo by Michal Soukup on Unsplash

Announcing our keynote speakers (drumroll, please!)
The opening keynote will be given by Max Welling, who is research chair in Machine Learning at the University of Amsterdam and a Distinguished Scientist at Microsoft Research. Prof. Welling will speak about graph neural networks and their use in knowledge representation and recommendation. The second keynote will be delivered by Natali Helberger, who is a Distinguished University Professor of Law and Digital Technology at the University of Amsterdam. Prof. Helberger will offer a legal perspective on recommender systems in a talk entitled: “Regulating Recommenders”. She will speak about the recent initiatives of the European Commission aimed at setting a standard for addressing the potential risks and opportunities of recommendation algorithms, and their world-wide implications. Our closing keynote will be given by Cynthia Liem, Associate Professor at Delft University of Technology and pianist of the Magma Duo. Her talk will provide a pianist’s perspective on recommendation, playing with the idea that a keynote should offer “key notes”. She will discuss conceptualizations of recommender systems and how we establish and sustain ‘what is worth promoting’.

Welcome to RecSys 2021
We are looking forward to welcoming you to RecSys 2021: first, informally at the Virtual Kickoff and, then, formally at the start of the main conference week on 27 September. We hope that you will enjoy hybrid RecSys 2021 and will use the Hub and its Library to access and interact with all the content that is presented during the main conference week.

Kind regards from the General Chairs,

Humberto, Martha, and Martijn




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