Published: 14th September 2023
DOI: 10.4204/EPTCS.387
ISSN: 2075-2180

EPTCS 387

Proceedings Combined 30th International Workshop on
Expressiveness in Concurrency
and 20th Workshop on
Structural Operational Semantics
Antwerp, Belgium, 18th September 2023

Edited by: Claudio Antares Mezzina and Georgiana Caltais

Preface Georgiana Caltais and Claudio Antares Mezzina
Invited Presentation: Timed Actors and Their Formal Verification Marjan Sirjani and Ehsan Khamespanah	1
Invited Contribution: EXPRESSing Session Types Ilaria Castellani, Ornela Dardha, Luca Padovani and Davide Sangiorgi	8
Invited Contribution: The Way We Were: Structural Operational Semantics Research in Perspective Luca Aceto, Pierluigi Crescenzi, Anna Ingólfsdóttir and Mohammad Reza Mousavi	26
Accepted Abstract: Comparing Deadlock-Free Session Processes, Revisited (Short Paper) Channa Dias Perera and Jorge A. Pérez	41
A Cancellation Law for Probabilistic Processes Rob van Glabbeek, Jan Friso Groote and Erik de Vink	42
A Lean-Congruence Format for EP-Bisimilarity Rob van Glabbeek, Peter Höfner and Weiyou Wang	59
Using Pi-Calculus Names as Locks Daniel Hirschkoff and Enguerrand Prebet	76
Deriving Abstract Interpreters from Skeletal Semantics Thomas Jensen, Vincent Rébiscoul and Alan Schmitt	97
Parallel Pushdown Automata and Commutative Context-Free Grammars in Bisimulation Semantics (Extended Abstract) Jos C. M. Baeten and Bas Luttik	114
Quantifying Masking Fault-Tolerance via Fair Stochastic Games Pablo F. Castro, Pedro R. D'Argenio, Ramiro Demasi and Luciano Putruele	132
CRIL: A Concurrent Reversible Intermediate Language Shunya Oguchi and Shoji Yuen	149

Preface

This volume contains the proceedings of EXPRESS/SOS 2023, the Combined 30th International Workshop on Expressiveness in Concurrency (EXPRESS) and the 20th Workshop on Structural Operational Semantics (SOS).

The first edition of EXPRESS/SOS was held in 2012, when the EXPRESS and SOS communities decided to organise an annual combined workshop bringing together researchers interested in the formal semantics of systems and programming concepts, and in the expressiveness of computational models. Since then, EXPRESS/SOS was held as one of the affiliated workshops of the International Conference on Concurrency Theory (CONCUR). Following this tradition, EXPRESS/SOS 2023 was held affiliated to CONCUR 2023, as part of CONFEST 2023, in Antwerp, Belgium. This year's edition marks two important anniversaries: EXPRESS turns 30 and SOS 20. In celebration of this dual anniversary, and to offer an overview of the past and future of these workshops, we are delighted to present two contributions from distinguished members of both communities in these proceedings:

EXPRESSing Session Types, by Ilaria Castellani, Ornela Dardha, Luca Padovani and Davide Sangiorgi;
The Way We Were: Structural Operational Semantics Research in Perspective, by Luca Aceto, Pierluigi Crescenzi, Anna Ingólfsdóttir and Mohammad Reza Mousavi.

The topics of interest for the EXPRESS/SOS workshop include (but are not limited to):

expressiveness and rigorous comparisons between models of computation;
expressiveness and rigorous comparisons between programming languages and models;
logics for concurrency; analysis techniques for concurrent systems;
comparisons between structural operational semantics and other formal semantic approaches;
applications and case studies of structural operational semantics;
software tools that automate, or are based on, structural operational semantics.

This volume contains revised versions of the 7 full papers and one abstract, selected by the Program Committee, as well as the following two invited papers, related to the topics presented by our invited speakers:

Formalizing Real World Programming Languages with Skeletal Semantics , by Alan Schmitt (INRIA, France);
Timed Actors and their Formal Verification, by Marjan Sirjani (Malardalen University, Sweden).

We would like to thank the authors of the submitted papers, the invited speakers, the members of the program committee, and their subreviewers for their contribution to both the meeting and this volume. We also thank the CONCUR 2023 and the CONFEST 2023 organizing committees for hosting the workshop. Finally, we would like to thank our EPTCS editor Rob van Glabbeek for publishing these proceedings and his help during the preparation.

Georgiana Caltais and Claudio Antares Mezzina,
August 2023

Program Committee

Valentina Castiglioni, Reykjavik University, Iceland
Matteo Cimini, University of Massachusetts Lowell, US
Cinzia Di Giusto, Université Côte d'Azur, France / CNRS, France
Wan Fokkink, Vrije Universiteit Amsterdam, The Netherlands
Sergey Goncharov, FAU Erlangen-Nürnberg, Germany
Tobias Kappé, Open University of the Netherlands and ILLC, University of Amsterdam, The Netherlands
Vasileios Koutavas, Trinity College Dublin, Ireland
Bas Luttik, Eindhoven University of Technology, The Netherlands
Hernán Melgratti, Universidad de Buenos Aires, Argentina
Mohammadreza Mousavi, King's College London, UK
Jorge A. Pérez, University of Groningen, The Netherlands
G. Michele Pinna, Università di Cagliari, Italy
Max Tschaikowski, Aalborg University, Denmark

Additional Reviewers

Andrea Esposito, Univerity of Urbino, Italy

Comparing Deadlock-Free Session Processes, Revisited (Short Paper)

Channa Dias Perera (University of Groningen)
Jorge A. Pérez (University of Groningen)

We are interested in type systems that enforce the deadlock-freedom property for pi-calculus processes. Several different type systems have been proposed, which consider different dialects of the pi-calculus and use different insights to rule out the circular dependencies that induce deadlocks.

Prior work by Dardha and P\'erez rigorously compared two kinds of type systems: (i) type systems based on priorities, as pioneered by Kobayashi; and (ii) type systems based on Curry-Howard interpretations of linear logic propositions as session types. They show that the former subsume the latter, i.e., type systems based on linear logic induce a class of deadlock-free processes that is strictly included in the class induced by priority-based systems. Dardha and P\'erez's comparison considers languages with similar (reduction) semantics, which admit the same definition of deadlock-freedom.

In our presentation, we report on ongoing work aimed at extending Dardha and P\'erez's classification to consider a class of deadlock-free processes with a self-synchronizing transition semantics, which is induced by presentations of linear logic based on hypersequents. Integrating this class into a formal comparison is interesting but subtle, as trivially deadlocked-processes in Dardha and P\'erez's setting actually enjoy the deadlock-freedom property under the self-synchronizing regime.