Combined 26th International Workshop on

Expressiveness in Concurrency

and 16th Workshop on

Structural Operational Semantics

Monday, August 26, 2019
Amsterdam, Netherlands
Affiliated with CONCUR 2019

Scope and Topics

The EXPRESS/SOS workshop series aims at bringing together researchers interested in the formal semantics of systems and programming concepts, and in the expressiveness of computational models.

Topics of interest for this combined workshop include (but are not limited to):

  • expressiveness and rigorous comparisons between models of computation (process algebras, event structures, Petri nets, rewrite systems)
  • expressiveness and rigorous comparisons between programming languages and models (distributed, component-based, object-oriented, service-oriented)
  • logics for concurrency (modal logics, probabilistic and stochastic logics, temporal logics and resource logics)
  • analysis techniques for concurrent systems
  • theory of structural operational semantics (metatheory, category-theoretic approaches, congruence results)
  • 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

We especially welcome contributions bridging the gap between the above topics and neighbouring areas, such as:

  • computer security
  • multi-agent systems
  • programming languages and formal verification
  • reversible computation
  • knowledge representation

Invited Speakers

Tom Hirschowitz

Savoie Mont Blanc University

Kirstin Peters

TU Berlin

Frank Valencia

Ecole Polytechnique de Paris
& Univ. Javeriana Cali.

The invited talk by Yuxin Deng, originally announced here, has been cancelled.



1 h

Tom Hirschowitz. Cellular monads from Positive GSOS specifications (invited talk)

We give a leisurely introduction to our abstract framework for operational semantics based on cellular monads on transition categories. Furthermore, we relate it for the first time to an existing format, by showing that all Positive GSOS specifications generate cellular monads whose free algebras are all compositional. As a consequence, bisimilarity is a congruence in all free algebras, which generalises the known result that bisimilarity in the standard, syntactic transition system is a congruence.

Chair: Jurriaan Rot


30 min

Coffee Break


30 min

Daniele Gorla, Ivano Salvo and Adolfo Piperno. Conflict vs Causality in Event Structures

Chair: Ilaria Castellani


30 min

Rob van Glabbeek. On the Meaning of Transition System Specifications


30 min

Tobias Prehn and Myron Rotter. Immediate Observation in Mediated Population Protocols


30 min

Omar Al Duhaiby and Jan Friso Groote. Distribution of Behaviour into Parallel Communicating Subsystems


1 h

Lunch Break


1 h

Kirstin Peters. Comparing Process Calculi Using Encodings (invited talk)

Encodings or the proof of their absence are the main way to compare process calculi. To analyse the quality of encodings and to rule out trivial or meaningless encodings, they are augmented with encodability criteria. There exists a bunch of different criteria and different variants of criteria in order to reason in different settings. This leads to incomparable results. Moreover, it is not always clear whether the criteria used to obtain a result in a particular setting do indeed fit to this setting. This talk provides a short survey on often used encodability criteria, general frameworks that try to provide a unified notion of the quality of an encoding, and methods to analyse and compare encodability criteria.

Chair: Jorge A. Pérez


30 min

Marino Miculan and Matteo Paier. A GSOS for Attribute-based Communication (short paper)


30 min

Coffee Break


1 h

Frank Valencia. Semantic Structures for Spatially-Distributed Multi-Agent Systems. (Invited talk)

In this talk I shall introduce an algebraic structure, which we call SCS (Spatial Constraint Systems), for specifying the epistemic behaviour of spatially-distributed multi-agent systems. In the systems under consideration agents have spaces (local stores) where they may have epistemic information (e.g., facts, beliefs, opinions), processes and other spaces. Agents communicate by using processes that can move epistemic information and other processes across different spaces.

SCS's can be seen as Scott's information systems with additional structure for specifying agents and their spaces. From a computational point of view SCS can be used to specify partial information holding in a given agent's space (local information). From an epistemic point of view SCS can be used to specify information that a given agent considers true (beliefs). They can also specify the mobility of information/processes from one space to another. They also provide for process/information extrusion, a central concept in formalisms for mobile communication from concurrency theory. From an epistemic point of view extrusion corresponds to a notion we shall call utterance; a piece of information that an agent communicates to others but that may be inconsistent with the agent’s beliefs (e.g., it may be a lie). SCS can also also be used to reason about distributed group information, understood as information that agents in group may potentially reach if they were to combine their local information.

SCS have been used as semantics structures for modal logic and spatial reactive programming languages. In this presentation I shall talk about SCS with emphasis on recent formal developments, in particular, theoretical and algorithmic results for computing the distributed information of a given group. I shall also discuss future work on modelling other group phenomena; namely group polarization.

Chair: Marino Miculan


30 min

Marco Bernardo. Coherent Resolutions of Nondeterminism (short paper)


The workshop proceedings are published as volume 300 of Electronic Proceedings in Theoretical Computer Science, available here and as a pdf.


Please register for EXPRESS/SOS 2019 via the registration page of CONCUR 2019.


We solicit two types of submissions:

  • Full papers of up to 15 pages excluding references (presented at the workshop and included in the proceedings)
  • Short papers of up to 5 pages excluding references (presented at the workshop, but not included in the proceedings)

Submission is performed through the EXPRESS/SOS 2019 EasyChair server.

Important Dates

June 28, 2019, AoE (extended deadline)

Paper submission

July 26, 2019

Notification to authors

August 11, 2019

Final version due

Programme Committee

  • Roberto Bruni, Università di Pisa
  • Ilaria Castellani, INRIA
  • Valentina Castiglioni, INRIA Saclay
  • Matteo Cimini, University of Massachusetts Lowell
  • Emanuele D'Osualdo, Imperial College London
  • Adrian Francalanza, University of Malta
  • Jean-Marie Madiot, INRIA
  • Marino Miculan, University of Udine
  • Mohammadreza Mousavi, University of Leicester
  • Jovanka Pantovic, University of Novi Sad
  • Jorge A. Pérez, University of Groningen (co-chair)
  • Jurriaan Rot, Radboud University (co-chair)
  • Erik de Vink, Eindhoven University of Technology


For questions, please contact:


The EXPRESS workshops aim at bringing together researchers interested in the expressiveness of various formal systems and semantic notions, particularly in the field of concurrency. Their focus has traditionally been on the comparison between programming concepts (such as concurrent, functional, imperative, logic and object-oriented programming) and between mathematical models of computation (such as process algebras, Petri nets, event structures, modal logics, and rewrite systems) on the basis of their relative expressive power. The EXPRESS workshop series has run successfully since 1994 and over the years this focus has become broadly construed. The SOS workshops aim at being a forum for researchers, students and practitioners interested in new developments, and directions for future investigation, in the field of structural operational semantics. One of the specific goals of the SOS workshop series is to establish synergies between the concurrency and programming language communities working on the theory and practice of SOS. Reports on applications of SOS to other fields are also most welcome, including: modelling and analysis of biological systems, security of computer systems programming, modelling and analysis of embedded systems, specification of middle-ware and coordination languages, programming language semantics and implementation, static analysis software and hardware verification, semantics for domain-specific languages and model-based engineering. Since 2012, the EXPRESS and SOS communities have joined forces and organised a combined EXPRESS/SOS workshop. The past combined workshops were a success, so this year there will again be a combined workshop on the semantics of systems and programming concepts, and on the expressiveness of mathematical models of computation. This year marks the 26th edition of EXPRESS and the 16th edition of SOS.

The EXPRESS workshops were originally held as meetings of the HCM project EXPRESS, which was active with the same focus from January 1994 till December 1997. The first three workshops were held respectively in Amsterdam (1994, chaired by Frits Vaandrager), Tarquinia (1995, chaired by Rocco De Nicola), and Dagstuhl (1996, co-chaired by Ursula Goltz and Rocco De Nicola). EXPRESS'97, which took place in Santa Margherita Ligure and was co-chaired by Catuscia Palamidessi and Joachim Parrow, was organized as a conference with a call for papers and a significant attendance from outside the project. EXPRESS'98 was held as a satellite workshop of the CONCUR'98 conference in Nice, co-chaired by Ilaria Castellani and Catuscia Palamidessi, and like on that occasion EXPRESS'99 was hosted by the CONCUR'99 conference in Eindhoven, co-chaired by Ilaria Castellani and Björn Victor. The EXPRESS'00 workshop was held as a satellite workshop of CONCUR 2000, Pennsylvania State University, co-chaired by Luca Aceto and Björn Victor. The EXPRESS'01 workshop was held at Aalborg University as a satellite of CONCUR'01 and was co-chaired by Luca Aceto and Prakash Panangaden. The EXPRESS'02 workshop was held at Brno University as a satellite of CONCUR'02 and was co-chaired by Uwe Nestmann and Prakash Panangaden. The EXPRESS'03 workshop was co-located with CONCUR 2003 in Marseille and was co-chaired by Flavio Corradini and Uwe Nestmann. The EXPRESS'04 workshop was co-located with CONCUR 2004 in London and was co-chaired by Jos Baeten and Flavio Corradini. The EXPRESS'05 workshop was co-located with CONCUR 2005 in San Francisco and was co-chaired by Jos Baeten and Iain Phillips. The EXPRESS'06 workshop was co-located with CONCUR 2006 in Bonn and was co-chaired by Roberto Amadio and Iain Phillips. The EXPRESS'07 workshop was co-located with CONCUR 2007 in Lisbon and was co-chaired by Roberto Amadio and Thomas Hildebrandt. The EXPRESS'08 workshop was co-located with CONCUR 2008 in Toronto and was co-chaired by Daniele Gorla and Thomas Hildebrandt. The EXPRESS'09 workshop was co-located with CONCUR 2009 in Bologna and was co-chaired by Sibylle Fröschle and Daniele Gorla. The EXPRESS'10 workshop was co-located with CONCUR 2010 in Paris and was co-chaired by Sibylle Fröschle and Frank Valencia. The EXPRESS'11 workshop was co-located with CONCUR 2011 in Aachen and was co-chaired by Bas Luttik and Frank Valencia.

The first SOS Workshop took place in London as one of the satellite workshops of CONCUR 2004. Subsequently, SOS 2005 occurred in Lisbon as a satellite workshop of ICALP 2005, SOS 2006 in Bonn as a satellite workshop of CONCUR 2006, SOS 2007 in Wroclaw as a satellite workshop of LICS and ICALP 2007, and SOS 2008 in Reykjavik as a satellite workshop of ICALP 2008. SOS 2009 was held as a satellite workshop of CONCUR 2009 in Bologna. SOS 2010 was held as a satellite workshop of CONCUR 2010 in Paris. Finally, SOS 2011 was held as a satellite workshop of CONCUR 2011 in Aachen.

The first combined EXPRESS/SOS workshop (EXPRESS/SOS 2012) was co-located with CONCUR 2012 in Newcastle upon Tyne, UK and was co-chaired by Bas Luttik and Michel Reniers. The second combined EXPRESS/SOS 2013 workshop was co-located with CONCUR 2013 in Buenos Aires, Argentina and was co-chaired by Johannes Borgström and Bas Luttik. The combined EXPRESS/SOS 2014 workshop was co-located with CONCUR 2014 in Rome, Italy and was co-chaired by Johannes Borgström and Silvia Crafa. The next year the combined EXPRESS/SOS 2015 workshop was co-located with CONCUR 2015 in Madrid, Spain and was co-chaired by Silvia Crafa and Daniel Gebler. The combined EXPRESS/SOS 2016 workshop was co-located with CONCUR 2016 in Québec City, Canada and was co-chaired by Daniel Gebler and Kirstin Peters. The combined EXPRESS/SOS 2017 workshop was co-located with CONCUR 2017 in Berlin, Germany and was co-chaired by Kirstin Peters and Simone Tini. The combined EXPRESS/SOS 2018 workshop was co-located with CONCUR 2018 in Beijing, China and was co-chaired by Jorge Perez and Simone Tini.

In these years some journal special issues dedicated to the mentioned events have been organised. A special issue of Journal of Logic and Algebraic Programming on Structural Operational Semantics appeared in 2004; a special issue of Theoretical Computer Science dedicated to SOS 2005 appeared in 2007, and a special issue of Information & Computation on Structural Operational Semantics inspired by SOS 2006-2007 appeared in 2009. Special issues devoted to EXPRESS 2010 and 2011 were both published in the journal Mathematical Structures in Computer Science. A special issue of the Acta Informatica dedicated to EXPRESS/SOS 2016-2017 is presently in progress.