PTHG-20: The Fourth Workshop on Progress Towards the Holy Grail

September 7, 2020, at CP2020, Louvain-la-Neuve, Belgium

This Workshop is one of a series.

Note: CP2020 and its workshops are virtual, with free registration.


In 1996 the paper “In Pursuit of the Holy Grail” (also here) proposed that Constraint Programming was well-positioned to pursue the Holy Grail of computer science: the user simply states the problem and the computer solves it. It was followed about a decade later by “Holy Grail Redux“, and then about a decade after that by “Progress Towards the Holy Grail“. This series of workshops aims to encourage and disseminate progress towards that goal, in particular regarding work on automating:

  • Problem Acquisition: learning, debugging, maintaining, etc. 
  • Model Reformulation: transformation for efficient solution, redundant models, etc. 
  • Solver Construction: adaptive parameter tuning, automated selection from portfolios, etc. 
  • User Explanation: reasons for failure, implications for choices, etc. 

Of special interest is the intersection of the Holy Grail goal with the increasing attention being paid to machine learning, explainable AI, Human-Aware AI, Human-AI Collaboration, and intelligent software assistants.


All times CEST (Central European Summer Time)

Session: Explanation (14:45 — 16:15)

14:45 — 15:15: Invited Talk. A Proof-Producing CSP Solver. Ofer Strichman. Technion – Israel Institute of Technology. Israel.

15:15 — 15:30: Paper: Explanation as Proof. Eugene C. Freuder. University College Cork. Ireland.

15:30 — 16:00: Invited Talk. Step-Wise Explanations for Constraint Satisfaction (and Optimization?). Bart Bogaerts. Vrije Universiteit Brussel. Belgium.

16:00 — 16:15: Discussion

Break (16:15 — 16:30)

Session: Acquisition, Modelling and Solving (16:30 — 18:00)

16:30 — 16:45: Paper. Using Unlabelled Examples in Constraint Acquisition. Steve Prestwich. University College Cork. Ireland.

16:45 — 17:00: Paper. On Correctness of Models and Reformulations. David Mitchell. Simon Fraser University. Canada.

17:00 — 17:15: Paper. Towards Unsatisfiable Core Learning for Chuffed. Ronald van Driel and Neil Yorke-Smith. Delft University of Technology, Netherlands.

17:15 — 17:45: Invited Talk. PDP: A General Neural Framework for Learning Constraint Satisfaction Solvers. Saeed Amizadeh. Microsoft. USA.

17:45 — 18:00: Discussion.

Organizing Committee:

Chair: Eugene Freuder, University College Cork, Ireland:

Narendra Jussien, École des Mines d’Albi-Carmaux, France

Lars Kotthoff, University of Wyoming, USA

Ian Miguel, University of St Andrews, Scotland


Submissions may be of any length, and in any format. They may be abstracts, position papers, technical papers, or demos. They may review your own previous work or survey a topic area. They may present new research or suggest directions for further progress. They may propose research roadmaps, demonstration domains, or collaborative projects. They may be proposals for measuring progress, and, in particular, for data sets or competitions to stimulate and compare progress. 

New this year: Previously Published Track. Authors may submit to this track relevant papers that have already been published elsewhere since the date of the last workshop, PTHG-19, September 30, 2019. The objective is to further the Workshop goal of disseminating progress in this area.

At least one author of every accepted submission must attend the workshop and pay the workshop fees; otherwise any presentation (and submission) will be withdrawn from the proceedings (if any) and program.

Standard submissions should be emailed, in PDF form, with subject line “PTHG-20 Submission”, directly to the Workshop chair, at:

Submissions to the Previously Published Track should be emailed similarly. These submissions should be clearly identified as submissions to the Previously Published Track, and bibliographic information provided on the previous publication. These submissions should contain either a PDF of the paper or a URL pointing to the full text of the paper, if these can be posted at the Workshop website without violating copyright. If not, a short PDF statement explaining the relevance of the paper to the Workshop, suitable for posting at the Workshop website, should be provided.

Authors may make multiple submissions if they wish. All submissions that appropriately address the topic of the workshop will be accepted as is, without further revision, and will be made available at the workshop website.

The deadline for submissions is August 3. Decisions on acceptance will be sent by August 7. If you submit at least two weeks before the early registration date for the conference, you will be sent a decision on acceptance at least one week before the early registration date for the conference.

Website: PTHG-20: The Fourth Workshop on Progress Towards the Holy Grail