ModRef 2023

The 22nd workshop on Constraint Modelling and Reformulation

August 27th, 2023; Part of CP 2023

ModRef 2023 is the 22nd in a series of workshops on Constraint Modelling and Reformulation organized as part of CP 2023, the 29th International Conference on Principles and Practice of Constraint Programming. It will be held on August 27th, directly preceding the CP conference.

The importance of modelling and model reformulation is widely recognised, particularly for CP but also for 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 constraint modelling, including new models or new modelling ideas for any amenable problem (whether a new application or a classic benchmark), constraint 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 constraint modelling or model reformulation.

Workshop topics include:

Important Dates

Paper Submission July 7th, 2023 July 11th AoE, 2023
Submissions may be updated until July 13th AoE, 2023
Notification of acceptance/rejection July 17th, 2023 July 21st, 2023
Camera ready version July 24th, 2023 TBC
Workshop day August 27th, 2023

Call for Papers

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: extended abstracts (at most two pages), short papers (at most eight pages) and long papers (at most fifteen pages). References are not part of the page limit. Papers are submitted through EasyChair, as a PDF file following LIPIcs guidelines. There is no requirement for papers to be anonymised before submission.

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.

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. The proceedings will be available electronically at CP 2023. Accepted contributions will be allowed a time slot for a presentation at the workshop. In-person presentation is preferable, but we will allow remote presentation of papers when necessary.


Session 1

Chair: Christopher Stone

9:00 – 9:30 Anna Latour, Arunabha Sen and Kuldeep Meel, Solving the Identifying Code Set Problem with Grouped Independent Support (Extended Abstract) (paper)

9:30 – 10:00 Joan Espasa Arxer, Ian Gent, Ian Miguel, Peter Nightingale, András Z. Salamon and Mateu Villaret, Towards a Model of Puzznic (paper)

10:00 – 10:30 Guillaume Derval and Damien Ernst, Symbolism for modelling, reformulations, and parallelism: MaxiCP-Modelling (paper)

Session 2

Chair: Christopher Stone

10:55 - 11:25 Sean Patterson, Joan Espasa, Mun See Chang and Ruth Hoffmann, Towards Automatic Design of Factorio Blueprints (paper)

11:25 - 11:55 Tias Guns, Things we underestimated while developing the CPMpy constraint modelling library (paper)

11:55 - 12:25 Miquel Bofill, Cristina Borralleras, Joan Espasa Arxer and Mateu Villaret, On Grid Graph Reachability and Puzzle Games (paper)

Session 3

13:40 - 14:10 Wout Vanroose, Ignace Bleukx, Jo Devriendt, Dimos Tsouros, Hélène Verhaeghe and Tias Guns, Breaking Constraint Modelling Languages with Metamorphic Testing (extended abstract) (paper)

14:10 - 15:10 Hélène Verhaeghe, Invited Talk: Solving Complex Problems: Graphs, Constraints, and Machine Learning in Action

Abstract: This talk is about a story on graphs. It started when I first stepped foot in research during my master’s thesis on the TSP. As I continued my path in research, graphs were still playing a big part as I designed my constraint propagators for the diagram constraint during my PhD at UCLouvain. Now, I mainly focus on hybridization techniques between CP and ML, but the graphs are still there, and even influence my design choices. During my talk, I’ll present my last projects, from my time as a post-doc at Polytechnique and now a post-doc at KULeuven, and how they are benefiting from underlying graph structures.

Session 4

Chair: Christopher Stone

15:30 – 16:30 Panel Discussion: What does the future hold for constraint modelling? Panel members: Hélène Verhaeghe, Peter Stuckey, Maria Garcia de la Banda.

Program Committee

Jip J. Dekker Monash University
Maria Andreina Francisco Rodriguez Uppsala University
Jimmy Lee The Chinese University of Hong Kong
Kevin Leo Monash University
Peter Nightingale (Chair) University of York
Christopher Stone (Chair) University of St Andrews
Guido Tack Monash University
Felix Ulrich-Oltean University of York

Special thanks to Kevin Leo and Jimmy Lee who made final decisions on papers where both chairs had a conflict of interest.