TERMGRAPH 2026

14th International Workshop on Computing with Terms and Graphs

Lisbon, Portugal

19 July 2026 (one-day workshop)

Part of FLoC 2026

News

Program of the workshop can now be found below. See also the FLoC version of the program for room information etc.

Background and history

Graphs, and graph transformation systems, are used in many areas within Computer Science: to represent data structures and algorithms, to define computation models, as a general modelling tool to study complex systems, etc.

Research in term and graph rewriting ranges from theoretical questions to practical implementation issues. Different research areas include: the modelling of first- and higher-order term rewriting by (acyclic or cyclic) graph rewriting, the use of graphical frameworks such as interaction nets and sharing graphs (optimal reduction), rewrite calculi for the semantics and analysis of functional programs, graph reduction implementations of programming languages, graphical calculi modelling concurrent and mobile computations, object-oriented systems, graphs as a model of biological or chemical systems, quantum computing, and automated reasoning and symbolic computation systems working on shared structures.

Previous editions of TERMGRAPH took place in Barcelona (2002), Rome (2004), Vienna (2006), Braga (2007), York (2009), Saarbrücken (2011), Rome (2013), Vienna (2014), Eindhoven (2016), Oxford (2018), online (2020, planned to be held in Paris), Haifa (2022), and Luxembourg (2024).

The permanent TERMGRAPH website has further information.

Aim

The aim of this workshop is to bring together researchers working in these different domains, to foster their interaction, to provide a forum for presenting new ideas and work in progress, and to enable newcomers to learn about current activities in this area.

Topics of Interest

Topics of interest include all aspects of term-/graph rewriting (term-graph and graph rewriting) and applications of graph transformations in programming, automated reasoning and symbolic computation. This includes (but is not limited to):

• theory of first-order and higher-order term and graph rewriting
• graph rewriting in lambda calculus (sharing graphs, optimality)
• term-/graph based models of computation
• graph grammars
• term-/graph based languages and modelling frameworks
• term-/graph rewriting tools:
  • system descriptions, and case studies
• applications of term-/graph rewriting in, and term-/graph rewriting aspects of:
  • semantics and implementation of programming languages
  • compiler construction
  • interaction nets and proof nets
  • string diagrams
  • software engineering
  • automated reasoning and symbolic computation
  • functional and logic programming
  • pattern recognition
  • Machine Learning (Graph Neural Networks)
  • bioinformatics
  • quantum computing

Call for Papers

We invite submissions of extended abstracts of at most 8 pages in EPTCS style (see also template on Overleaf). This may include, concerning any of the topics above:

• original work,
• tutorials,
• work in progress,
• system descriptions of term-/graph rewriting tools.

Extended abstracts have to be submitted no later than 27 April 2026 (AoE) electronically (pdf) via:

• the FLoC HotCRP submission site: https://submissions.floc26.org/termgraph/.

Papers will be judged on relevance, originality, correctness, and usefulness.

After the workshop, authors of presented extended abstracts will be invited to submit a longer version of their work (a 15-page paper) for the publication of the Workshop Post-Proceedings in EPTCS (Electronic Proceedings in Theoretical Computer Science) These submissions will undergo a second round of refereeing with:

• submission deadline in the mid of October 2026,
• notification in December 2026,
• publication in February 2027.

Important Dates (AoE)

• Extended submission deadlines:
  • Titles and short abstracts: Wednesday, 6 May 2026
  • Extended abstracts: Monday, 11 May 2026
• Notification: Wednesday, 27 May 2026
• Program publication: Wednesday, 3 June 2026
• Final pre-proceedings version (8 pages excluding references) due: Monday, 15 June 2026
• Workshop: 19 July 2026

Invited Speakers

• Dan R. Ghica, Huawei Central Software Institute & University of Birmingham, UK (Joint keynote with DIALOCO 2026)
  Syntactic trinitarianism: terms, graphs, diagrams

  The concept of 'syntax' is commonly understood as the structure hidden in linear sequences of tokens, which in language and logic we commonly call ‘terms’. However, for the purpose of analysis and transformation, compilers use more efficient data structures to represent syntax, namely graphs. The gap between the linear (term) and graph syntax is elegantly bridged by a third formalism, namely that of string diagrams, a planar representation of terms in the categorical representation of syntax. In this talk I will show how the interplay of terms, graphs, and diagrams can help specify and implement complex analyses and transformations in compilers for higher-order programming languages, such as type inference, automatic differentiation, or closure conversion. This methodology is at the foundation of a new industrial-strength compiler being implemented currently at Huawei.
  Most of the material I will discuss is based on the recent tutorial paper “Hierarchical string diagrams and applications” jointly with Fabio Zanasi (https://arxiv.org/abs/2305.18945) about to appear as a CUP monograph.

• Nicolas Troquard, Gran Sasso Science Institute, Italy
  Graph Neural Networks, Their Logics, and Formal Verification

  Graph Neural Networks are deep learning models designed to process graph-structured data. Most modern GNNs operate by message passing: node representations are updated through repeated rounds of aggregating and combining information from neighboring nodes. This makes them well suited to applications involving relational and networked structures, and also places them naturally in dialogue with topics from graph rewriting and graph-based computation.
  In this talk, we present recent results on the relationship between Graph Neural Networks and formal logic, with the choice of topics guided by the speaker's own research in the area. We introduce logics that precisely capture the expressive power of certain classes of integer-valued GNNs, and show how GNN computations can be translated into logical formulas. We also discuss variants of GNNs over finite computer number formats. These logical characterizations provide a foundation for formal verification, allowing us to establish complexity bounds for key reasoning problems about GNN behavior.

• Vincent van Oostrom, University of Sussex, UK
  Term graph rewriting for implementing the λ-calculus refactored

  We retrace some history of using term graphs for implementing β-reduction in the λ-calculus. We refactor the following three high-lights from that history, illustrated by a prototype implementation:

  • the classical (first) term graph implementation (Wadsworth), of β-reduction which we refactor through a term graph implementation IMP of a well-behaved (e.g., orthogonal) class of TRSs;
  • implementing β-reduction through repeated weak-reduction (De Bruijn (Automath), Peyton Jones, Coquand, Grégoire & Leroy, Balabonski,...), which we show can be performed on IMP;
  • implementing needed β-reduction (Huet & Lévy, Barendregt, Kennaway, Klop, Sleep,...) through a strategy for IMP that we dub α-spine. By making use of union-find techniques for it, normal order reduction is shown to be linearly implementable.

Programme

Session 1

9:00 - 10:00 (Joint keynote with DIALOCO 2026)
Dan R. Ghica (Huawei Central Software Institute & University of Birmingham, UK)
Syntactic trinitarianism: terms, graphs, diagrams

Coffee Break & Room Change

Session 2

10:30 - 11:30 (invited talk)
Nicolas Troquard (Gran Sasso Science Institute, Italy)
Graph Neural Networks, Their Logics, and Formal Verification

11:30 - 12:00
Marc Thatcher (University of Sussex, UK)
A Programming Language for Interaction Nets (Extended Abstract)

12:00 - 12:30
Pedro Cunha, Sandra Alves and Mário Florido (Faculdade de Ciˆencias da Universidade do Porto, Portugal)
Labels, paths and linearization of the λ -calculi (Extended Abstract)

Lunch

Session 3

14:00 - 15:00 (invited talk)
Vincent van Oostrom (University of Sussex, UK)
Term graph rewriting for implementing the λ-calculus refactored

15:00 - 15:30
Anna Matsui (Johns Hopkins University, USA) and Koko Muroya (Ochanomizu University, Japan)
Hypergraphs with Binding (Extended Abstract)

Coffee Break

Session 4

16:00 - 16:30
Dale Miller (Inria Saclay and LIX, Institut Polytechnique de Paris, France)
Relating ordered hypergraph rewriting and proof theory: Work in progress (Extended Abstract)

16:30 - 17:00
Bastiaan Laarakker and Tobias Kappé (LIACS, Leiden University, The Netherlands)
Reducible Graphs and Bisimilarity of 1-free Star Expressions (Extended Abstract)

17:00 - 17:30
Clemens Grabmayer (Gran Sasso Science Institute, Italy)
Towards a Characterisation of the Graph Structure of Process Interpretations of Regular Expressions (Extended Abstract)

17:30 - closing

Registration

Registration to the workshop is open and possible via the FLoC registration page.

Program Committee

• Koko Muroya, Ochanomizu University, Japan (co-chair)
• Kazunori Ueda, Waseda University, Japan (co-chair)
• Sandra Alves, University of Porto, Portugal
• Clemens Grabmayer, Gran Sasso Science Institute, Italy
• Amar Hadzihasanovic, Tallinn University of Technology, Estonia
• Makoto Hamana, Kyushu Institute of Technology, Japan
• Jens Kosiol, Philipps-Universität Marburg, Germany
• Robin Piedeleu, University College London, UK
• Chris Poskitt, Singapore Management University, Singapore
• Femke van Raamsdonk, Vrije Universiteit Amsterdam, Netherlands
• Michele Sevegnani, University of Glasgow, UK