View source for 21st International Workshop on Termination

July 25, 2026, Lisbon, Portugal.

As part of [https://www.floc26.org FLoC 2026] and
co-located with [https://www.floc26.org/ijcar IJCAR 2026].



==Background==

The Workshop on Termination (WST) traditionally brings together, in an
informal setting, researchers interested in all aspects of termination,
whether this interest be practical or theoretical, primary or derived. 
The workshop also provides a ground for cross-fertilization of ideas from 
the different communities interested in termination (e.g., working on 
computational mechanisms, programming languages, software engineering, 
constraint solving, etc.). The friendly atmosphere enables fruitful 
exchanges leading to joint research and subsequent publications.

The 21st International Workshop on Termination (WST 2026) continues
the successful workshops held in
St. Andrews (1993), 
La Bresse (1995), 
Ede ([http://www-i2.informatik.rwth-aachen.de/giesl/WST97/main.html 1997]), 
Dagstuhl ([http://verify.rwth-aachen.de/giesl/WST99.html 1999]), 
Utrecht ([http://www.cs.tau.ac.il/~nachumd/wst/index.html 2001]), 
Valencia ([http://users.dsic.upv.es/~rdp03/wst/ 2003]), 
Aachen ([http://www-i2.informatik.rwth-aachen.de/WST04/ 2004]), 
Seattle ([https://www.illc.uva.nl/LogicList/newsitem.php?id=1416 2006]), 
Paris ([http://www.lsv.fr/Events/rdp07/wst.html 2007]), 
Leipzig ([http://www.imn.htwk-leipzig.de/~waldmann/wst09/cfp/WST09_cfp.pdf 2009]),
Edinburgh ([http://www.floc-conference.org/WST-home.html 2010]), 
Obergurgl ([http://cl-informatik.uibk.ac.at/users/georg/events/wst2012/ 2012]), 
Bertinoro ([http://www.imn.htwk-leipzig.de/WST2013/ 2013]), 
Vienna ([http://easychair.org/smart-program/VSL2014/WST-index.html 2014]),
Obergurgl ([http://cl-informatik.uibk.ac.at/events/wst-2016/ 2016]),
Oxford ([http://wst2018.webs.upv.es/ 2018]),
virtually ([http://costa.fdi.ucm.es/wst2021/ 2021]),
Haifa ([https://sws.cs.ru.nl/WST2022 2022]),
Obergurgl ([https://termination-portal.org/wiki/19th_International_Workshop_on_Termination 2023]), and
Leipzig ([https://www.imn.htwk-leipzig.de/WST2025/ 2025]).

==Workshop Topics==

The 21st International Workshop on Termination welcomes contributions 
on all aspects of termination. In particular, papers investigating applications 
of termination (for example in complexity analysis, program analysis and
transformation, theorem proving, program correctness, modeling computational 
systems, etc.) are very welcome.

Topics of interest include (but are not limited to):

* termination and complexity analysis in any domain (lambda calculus, declarative programming, rewriting, transition systems, probabilistic programs, etc.)
* abstraction methods in termination analysis
* certification of termination and complexity proofs
* challenging termination problems
* comparison and classification of termination methods
* implementation of termination and complexity methods
* non-termination analysis and loop detection
* normalization and infinitary normalization
* operational termination of logic-based systems
* ordinal notation and subrecursive hierarchies
* SAT, SMT, and constraint solving for (non-)termination analysis
* scalability and modularity of termination methods
* well-founded relations and well-quasi-orders

==Termination Competition==

Since 2003, the catalytic effect of WST to stimulate new research
on termination has been enhanced by the celebration of the [[Termination_Competition]] 
and its continuously developing problem databases containing thousands of programs 
as challenges for termination analysis in different categories.
In 2026, the Termination Competition will run live (in parallel to the FLoC workshops, on the 24th and 25th of July). <!--Tool/benchmark authors are invited to submit a short tool paper and give a presentation on the workshop.-->

<!--

==Keynote Speaker==

[https://quave.cs.uni-saarland.de/benjamin-kaminski/ Benjamin Kaminski], Saarland U.
<b>Termination of Probabilistic Programs</b>

<b>Abstract</b>
Unlike for ordinary programs, termination of probabilistic programs is more nuanced: A probabilistic program can terminate with probability 1 while still needing infinitely many computation steps in expectation. We will explore the complexity landscape of probabilistic program termination and present proof rules for proving both almost-sure termination (i.e. termination with probability 1) as well as positive almost-sure termination (i.e. termination within finite expected time). Time permitting, we will furthermore dive into open problems on termination of weighted programs – a generalization of probabilistic programs where branches can be associated with more general weights from a semiring.

==Program==

===Thursday 24 August===

'''Session 1''': Keynote & Probabilistic Termination (Chair: Akihisa Yamada)
{|
|-
|style="vertical-align:top;"|14:00
|	[https://quave.cs.uni-saarland.de/benjamin-kaminski/ Benjamin Kaminski]:
	'''Termination of Probabilistic Programs <span style="color:red;">(invited talk)</span>'''
|-
|style="vertical-align:top;"|15:00
|	<u>Jan-Christoph Kassing</u> and [https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]:
	'''Dependency Tuples for Almost-Sure Innermost Termination of Probabilistic Term Rewriting''' [https://doi.org/10.48550/arXiv.2307.10002 (paper)]
|-
|style="vertical-align:top;"|15:30
|	coffee break
|}

'''Session 2''': Termination of Term Rewriting (Chair: Johannes Waldmann)
{|
|style="vertical-align:top;"|16:00
|	<u>Fabian Mitterwallner</u>, Aart Middeldorp and René Thiemann:
	'''Linear Termination over N is Undecidable''' [https://doi.org/10.48550/arXiv.2307.14805 (paper)]
|-
|style="vertical-align:top;"|16:30
|	Teppei Saito and Nao Hirokawa:
	'''Generalizing Weighted Path Orders''' [https://doi.org/10.48550/arXiv.2307.13973 (paper)]
|-
|style="vertical-align:top;"|17:00
|	<u>René Thiemann</u> and Elias Wenninger:
	'''A Verified Efficient Implementation of the Weighted Path Order''' [https://doi.org/10.48550/arXiv.2307.14671 (paper)]
|-
|style="vertical-align:top;"|17:30
|	<u>Nao Hirokawa</u> and Aart Middeldorp:
	'''Hydra Battles and AC Termination, Revisited''' [https://doi.org/10.48550/arXiv.2307.14036 (paper)]
|-
|18:00
|
----
|}

===Friday 25 August===

'''Session 3''': Termination beyond Term Rewriting (Chair: Carsten Fuhs)
{|
|style="vertical-align:top;"|9:00
|	Ayuka Matsumi, Naoki Nishida, Misaki Kojima and Donghoon Shin:
	'''On Singleton Self-Loop Removal for Termination of LCTRSs with Bit-Vector Arithmetic''' [https://doi.org/10.48550/arXiv.2307.14094 (paper)]
|-
|style="vertical-align:top;"|9:30
|	Liye Guo and Cynthia Kop:
	'''Higher-Order LCTRSs and Their Termination''' [https://doi.org/10.48550/arXiv.2307.13519 (paper)]
|-
|style="vertical-align:top;"|10:00
|	Jera Hensel and <u>[https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]</u>:
	'''Automated Termination Proofs for C Programs with Lists''' [https://doi.org/10.48550/arXiv.2307.11024 (paper)]
|-
|style="vertical-align:top;"|10:30
|	coffee break
|}

'''Session 4''': Non-Termination (Chair: René Thiemann)
{|
|style="vertical-align:top;"|11:00
|	Dieter Hofbauer and Johannes Waldmann:
	'''Old and New Benchmarks for Relative Termination of String Rewrite Systems''' [https://doi.org/10.48550/arXiv.2307.14149 (paper)]
|-
|style="vertical-align:top;"|11:30
|	<u>[https://ffrohn.github.io Florian Frohn]</u> and [https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]:
	'''Proving Non-Termination by Acceleration Driven Clause Learning''' [https://doi.org/10.48550/arXiv.2307.09839 (paper)]
|-
|style="vertical-align:top;"|12:00
|	[http://lim.univ-reunion.fr/staff/epayet/ Étienne Payet]:
	'''Binary Non-Termination in Term Rewriting and Logic Programming''' [https://doi.org/10.48550/arXiv.2307.11549 (paper)]
|-
|style="vertical-align:top;"|12:30
|	lunch
|}

'''Session 5''': Complexity Analysis and Probabilistic termCOMP (Chair: Benjamin Kaminski)
{|
|style="vertical-align:top;"|14:00
|	<u>Nils Lommen</u>, Eleanore Meyer and [https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]:
	'''Automated Complexity Analysis of Integer Programs via Triangular Weakly Non-Linear Loops''' [https://doi.org/10.48550/arXiv.2307.10061 (paper)]
|-
|style="vertical-align:top;"|14:30
|	Cynthia Kop and Deivid Vale:
	'''Complexity Analysis for Call-by-Value Higher-Order Rewriting''' [https://doi.org/10.48550/arXiv.2307.13426 (paper)]
|-
|style="vertical-align:top;"|15:00
|	'''0th Probabilistic termCOMP'''
|-
|style="vertical-align:top;"|15:30
|	coffee break
|}

'''Session 6''': termCOMP 2023 and business meeting (Chair: Akihisa Yamada)
{|
|style="vertical-align:top;"|16:00
|	<u>Nils Lommen</u>, Eleanore Meyer and [https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]:
	'''KoAT: An Automatic Complexity Analysis Tool for Integer Programs'''
|-
|style="vertical-align:top;"|16:15
|	<u>[https://ffrohn.github.io Florian Frohn]</u> and [https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]:
	'''Proving Non-Termination and Lower Runtime Bounds via ADCL with LoAT'''
|-
|style="vertical-align:top;"|16:30
|	<u>[https://verify.rwth-aachen.de/giesl/ Jürgen Giesl]</u>, Daniel Cloerkes, Stefan Dollase, [https://ffrohn.github.io Florian Frohn], Carsten Fuhs, Jera Hensel, Jan-Christoph Kassing, Nils Lommen and Eleanore Meyer:
	'''AProVE 2023'''
|-
|style="vertical-align:top;"|16:45
|	Fred Mesnard and <u>[http://lim.univ-reunion.fr/staff/epayet/ Étienne Payet]</u>:
	'''NTI+cTI: a Logic Programming Termination Analyzer'''
|-
|style="vertical-align:top;"|17:00
|	Dieter Hofbauer:
	'''MultumNonMulta entering Term Rewriting'''
|-
|style="vertical-align:top;"|17:15
|	[https://akihisayamada.github.io/ Akihisa Yamada]:
	'''Results of the [[Termination Competition 2023]]'''
|-
|style="vertical-align:top;"|17:30
|	'''business meeting'''
|}

-->

==Submission Guidelines==

Submissions are short papers/extended abstracts which should not exceed 5 pages.
There will be no formal reviewing. In particular, we welcome short versions of recently published articles and papers
submitted elsewhere. The program committee checks relevance and provides additional feedback for each submission.
The accepted papers will be made available electronically before the workshop.

Papers should be submitted electronically via
[https://submissions.floc26.org/wst/ the submission page].

Please use LaTeX and
[https://www.dagstuhl.de/en/publishing/series/details/LIPIcs the LIPIcs style file]
to prepare your submission.

==Important Dates==

TBA

<!--
* title and abstract submission: <s>June 1</s>
* paper submission: <s>June 8</s>
* notification: <s>June 15</s>
* final version: <s>July 27</s>
* workshop: August 24-25
-->

==Program Committee==

TBA

<!--
* [http://www-sop.inria.fr/members/Martin.Avanzini/ Martin Avanzini], INRIA Sophia Antipolis
* [https://ffrohn.github.io/ Florian Frohn], RWTH Aachen
* [https://www.dcs.bbk.ac.uk/~carsten/ Carsten Fuhs], Birkbeck, U. London
* [https://raulgut.github.io/ Raúl Gutiérrez], U. Politécnica de Madrid
* [http://lim.univ-reunion.fr/staff/epayet/ Étienne Payet], U. La Réunion
* [https://costa.fdi.ucm.es/~arubio/ Albert Rubio], Complutense U. Madrid
* [http://cl-informatik.uibk.ac.at/users/thiemann/ René Thiemann], U. Innsbruck
* [https://deividrvale.github.io/ Deivid Vale], Radboud U. Nijmegen
* [https://www.imn.htwk-leipzig.de/~waldmann/index.html Johannes Waldmann], HTWK Leipzig
* [https://akihisayamada.github.io/ Akihisa Yamada], AIST Tokyo Waterfront (chair)
-->