ModRef 2026 is the 25th in a series of workshops on Constraint Modelling and Reformulation (see some past contributions) and is organized as part of CP 2026 the 32nd International Conference on Principles and Practice of Constraint Programming, held this year in Lisbon, Portugal. ModRef will be held on July 19th 2026, which is the day before the main CP conference begins. ModRef and CP are part of FLOC 2026, a four-yearly co-location of conferences and workshops related to logic in computer science.
The importance of modelling and model reformulation is widely recognised in many domains, such as for CP, MIP, SAT, SMT and other kinds of general-purpose solvers. There has been significant research effort in recent years into modelling and model reformulation, such as automating techniques used by expert modellers, and developing tools and techniques to target multiple types of solvers from one model.
The purpose of ModRef is to be a forum for all kinds of work in modelling, including new models or new modelling ideas for any amenable problem (whether a new application or a classic benchmark), reformulation techniques to improve the performance of models when solved by general-purpose solvers, and automated modelling techniques, tools, and languages. We solicit original papers that contribute to the understanding of modelling or model reformulation.
Workshop topics include:
Registration will be available through the FLoC 2026 registration page
| Abstract Submission | |
| Paper Submission | 15 May 2026 |
| Notification of acceptance/rejection | 25 May 2026 |
| Camera ready version | 5 July 2026 |
| Workshop day | 19 July 2026 |
This year ModRef will again accept paper submissions. In addition to the presentation of research results, we especially welcome submissions of novel (ongoing) work, recent breakthroughs, future directions, and descriptions of interesting aspects of existing systems.
There are three types of paper submissions:
References and appendices are not part of the page limit. We also accept (and encourage) non-traditional electronic submissions, such as interactive works/tool demonstrations. In this case, please contact the chairs to discuss the suitability of your submission for ModRef.
Papers should be submitted through HotCRP as PDF files following LIPIcs guidelines. There is no requirement for papers to be anonymised before submission.
All submissions will be reviewed, and those that are well-written and make a worthwhile contribution to the topic of the workshop will be accepted for publication in the workshop proceedings, which will be available electronically on this website. Accepted contributions will be allowed a time slot for a presentation at the workshop.
Paper submission link: https://submissions.floc26.org/modref
TBA
| 09:00-09:10 | Opening Chair: Jordi Coll |
| 09:00-09:10 | Welcome and Introduction Jordi Coll (Universitat de Girona) |
| 09:10-10:30 | Session 1: Constraint Modelling and Propagation |
| 09:10-09:30 | Defining Propagators in MiniZinc. Jip J. Dekker, Peter J. Stuckey, Guido Tack, Huu Quang Tran, Markus Wagner |
| 09:30-09:50 | Propagation Algorithms for the Minimum-Distance Constraint over Selected Points Mikael Zayenz Lagerkvist |
| 09:50-10:10 | Machine Learning-Based Generalization Queries for Constraint Acquisition Dimos Tsouros, Senne Berden, Tias Guns |
| 10:10-10:30 | Paramita: An Extensible Framework for SATisfiability Solving Josep Alòs, Carlos Ansótegui, Juan Luis Esteban, Eduard Torres |
| 10:30-11:00 | Coffee Break |
| 11:00-11:40 | Session 2: Puzzles |
| 11:00-11:20 | An Interactive Application to Solve Sudoku Variant Puzzles Helmut Simonis, Luis Quesada |
| 11:20-11:40 | Scaling Sudoku as a Constraint Problem Mikael Zayenz Lagerkvist |
| 11:40-12:20 | Invited Talk |
| 11:40-12:20 | TBA |
| 12:20-13:50 | Lunch Break |
| 13:50-14:30 | Session 3: Automated Generation and Reformulation |
| 13:50-14:10 | Computing Gadgets Josep Alòs, Carlos Ansótegui, Supratik Chakraborty, Eduard Torres |
| 14:10-14:30 | Towards Automated Generation of Benchmark Instances with Diverse Solver Performance Tianchen Wu, Ian Miguel, Nguyen Dang |
| 14:30-15:20 | To Be Confirmed |
| 15:20-15:50 | Coffee Break |
| 15:50-17:00 | Session 4: Applications |
| 15:50-16:00 | Novel Pair- and Topic-Swapping Frej Knutar Lewander, Jennifer Jennifer Gross, María Andreína Francisco Rodríguez |
| 16:00-16:20 | No More Awkward Silences with Table Talk Tuning Martin Butler, Mikael Zayenz Lagerkvist |
| 16:20-16:40 | A Simple Yet Efficient Lifted Formulation for Hard-to-Ground Planning Problems Miquel Bofill, Cristina Borralleras, Josu Oca |
| 16:40-17:00 | Automated grading of student constraint models Hendrik Bierlee, Tias Guns |
| Jordi Coll (Chair) | Universitat de Girona |
| Felix Ulrich-Oltean (Chair) | University of York |
| Özgür Akgün | University of St Andrews |
| Carlos Ansótegui | Universitat de Lleida |
| Hendrik Bierlee | KU Leuven |
| Mun See Chang | University of St Andrews |
| Sami Cherif | Université de Picardie Jules Verne |
| Jip Dekker | Monash University |
| Emir Devirović | Delft University of Technology |
| Joan Espasa Arxer | University of St Andrews |
| María Andreína Francisco Rodríguez | Uppsala University |
| Ian Gent | University of St Andrews |
| Ramiz Gindullin | Uppsala University |
| Tias Guns | KU Leuven |
| Emmanuel Hebrard | Université de Toulouse |
| Christopher Jefferson | University of St Andrews |
| George Katsirelos | INRAE |
| Kevin Leo | Monash University |
| Peter Nightingale | University of York |
| Justin Pearson | Uppsala University |
| Gilles Pesant | Polytechnique Montréal |
| Pierre Schaus | UC Louvain |
| Christine Solnon | INSA Lyon |
| Bernardo Subercaseaux | Carnegie Mellon University |
| Mateu Villaret | Universitat de Girona |
| Allen Zhong | Monash University |