PODC

Welcome to the 40th ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing (PODC 2021), held virtually (due to the COVID-19 pandemic) on July 26-30, 2021. PODC is the premier forum for presentation of research on all aspects of distributed computing, including the theory, design, implementation, and applications of distributed algorithms, systems, and networks.

This volume contains 44 regular papers and 14 brief announcements selected by the Program Committee for presentation at PODC 2021, as well as the abstracts of two keynote lectures and three tutorials. The volume also includes the citations for two awards jointly sponsored by PODC and the EATCS Symposium on Distributed Computing (DISC): the Edsger W. Dijkstra Prize in Distributed Computing, and the Principles of Distributed Computing Doctoral Dissertation Award.

The 2021 Edsger W. Dijkstra Prize in Distributed Computing will be presented at DISC 2021 to Paris C. Kanellakis (posthumously) and Scott A. Smolka for their paper "CCS Expressions, Finite State Processes, and Three Problems of Equivalence". The 2021 Principles of Distributed Computing Doctoral Dissertation Award will be presented at PODC 2021 to Dr. Leqi Zhu, for his dissertation titled "On the Space Complexity of Colourless Tasks," and to Dr. Goran Zuzic, for his dissertation titled "Towards Universal Optimality in Distributed Optimization."

This year, 172 regular papers and 20 brief announcements were submitted to the symposium, where some regular submissions asked to be considered also as brief announcements. The Program Committee accepted 44 papers and 14 brief announcements that cover a wide variety of topics. Every submitted paper was read and evaluated by at least three reviewers. Approximately half of the submissions were retained for a second phase, during which one or two additional committee members reviewed each paper. The final decisions regarding acceptance were made in a meeting held on April 26-27, 2021, via videoconferencing. Revised and expanded versions of a few selected papers will be considered for publication in a special issue of the journal Distributed Computing and in the Journal of the ACM.

The Best Paper Award was presented to Greg Bodwin and Merav Parter for their paper "Restorable Shortest Path Tiebreaking for Edge-Faulty Graphs".

The program included two keynote talks: Cynthia Dwork talked about "Differential Privacy in Distributed Environments: An Overview and Open Questions", and Kyle Kingsbury talked about "Elle: Finding Isolation Violations in Real-World Databases".

This year, the program also initiated a new concept called a Gem Session, whose aim is to present a gem in one of PODC's topics of interest and relate it to current research directions, for the sake of bringing together researchers in the various subareas of PODC. There were two gem sessions: Naama Ben-David talked about "Classic Consensus Impossibilities in Modern Byzantine Fault Tolerance", and Laurent Feuilloley talked about "How to locally certify a global property? From spanning trees to planar graphs, and beyond".

Three workshops were co-located with PODC: Workshop on Advanced Tools, Programming Languages, and Platforms for Implementing and Evaluating Algorithms for Distributed Systems (ApPLIED), Biological Distributed Algorithms (BDA), and Distributed Algorithms on Realistic Network Models (DARe).