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:

• Application papers describing interesting problems and interesting ways to model them;
• Contributions to understanding modelling that could guide the manual or automatic formulation of models;
• Identification of the criteria that should be used in evaluating models and the design of pragmatic techniques that facilitate the choice and possible combination among alternative models;
• Design of higher-level modelling languages;
• Automatic reformulation techniques; and
• Techniques which allow automatically targeting multiple kinds of solvers from a single declarative model.

Registration

Registration will be available through the FLoC 2026 registration page

Important Dates

Abstract Submission	8 May 2026
Paper Submission	15 May 2026
Notification of acceptance/rejection	25 May 2026
Camera ready version	5 July 2026
Workshop day	19 July 2026

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.
• Long papers: at most fifteen pages.

References 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

Invited Talk

TBA

Accepted Papers

TBA

Schedule

TBA

Program Committee

Jordi Coll (Chair)	Universitat de Girona
Felix Ulrich-Oltean (Chair)	University of York

Full PC TBA