Constraint Handling Rules

In a recent project, Fraunhofer Institute uses CHR for semantic analysis in voice-controlled systems. As part of the project Speech Assistance for Citizen Services (S4CS), the conversation logic is modelled in CHR. This approach is fast, flexible, and can be adapted for different dialogue scenarios. The system uses GoCHR, a new CHR interpreter written in the Go programming language.

VanDeGraphGenerator, an AI that generates abstract art, was selected as official contribution to the German Science Year 2019 on Artificial Intelligence of the Federal Ministry of Education and Research. More information in this article on the project’s website.

The computer software VanDeGraphGenerator analyses, generates and visualizes line graphics. We used the VanDeGraphGenerator algorithm to classify and generate designs for mason’s marks. Now an extension of VanDeGraphGenerator VdGG+ turns this medieval craftsmanship into contemporary abstract digital art. More information on https://www.ai-art.info/.

The book “Constraint Handling Rules – Compilation, Execution, and Analysis” has a new edition, because the old one is out of print. By popular request, the book format has been enlarged. See Google Books.

A preliminary version of the survey on Parallelism, Concurrency and Distribution in Constraint Handling Rules is online:

https://arxiv.org/abs/1703.10959

Comments are welcome!

As a PC-member I encourage submissions to

34th International Conference on Logic Programming (ICLP 2018)
Oxford, UK, July 14-17, 2018
http://www.logicprogramming.org/iclp2018

ICLP is the premier conference on foundations and applications of logic programming, including but not restricted to answer-set programming, non-monotonic reasoning, unification and constraints based logic languages, constraint handling rules, argumentation logics, deductive databases, description logics, inductive and co-inductive logic programming.

• Type inference for datalog with complex type hierarchies
  US Patent 2017
  What is disclosed are a novel system and method for inferring types of database queries.
• Editing and compiling business rules
  US Patent 2017
  A component in a graph-based computation having data processing components connected by linking elements representing data flows is updated by receiving a rule specification…
• Soft constraints in scheduling
  US Patent 2012
  A method for implementing soft constraints in scheduling comprises receiving a description of circuit behavior.
• User programmable deductive spreadsheet apparatus…
  US Patent 2010
  A user programmable deductive spreadsheet is implemented as an add-in to an existing mathematical spreadsheet program…
• Integrating optimization directly into databases
  US Patent 2009
  Systems, methods and articles solve computationally complex problems. Example embodiments provide data query language features that may be used to express optimization problems.
• Position display system of mobile terminal
  US Patent 2002
  A position detection system of a mobile terminal includes a small zone communication system such as the PHS system, and a center station connected to an exchange station forming the PHS system.

As a PC-member I strongly welcome submissions dealing with Constraint Handling Rules at these fine conferences:

19th International Symposium on Principles and Practice of Declarative Programming (PPDP),
Namur, Belgium, 9 Oct. – 11 Oct. 2017.
http://complogic.cs.mcgill.ca/ppdp2017/

International Joint Conference on Rules and Reasoning (RuleML+RR 2017),
London, UK from 12-15th July 2017.
http://2017.ruleml-rr.org/

21st International Conference on Logic for Programming, Artificial Intelligence and Reasoning,
Maun, Botswana, at Cresta Riley’s Hotel, 7-12th May 2017.
http://easychair.org/smart-program/LPAR-21/

And another fine conference:

33rd International Conference on Logic Programming (ICLP 2017),
Melbourne, Australia, August 29 to September 1, 2017.
http://iclp17.a4lp.org/

Yesterday Jan Wielemaker published version 7.3.28 of SWI-Prolog. It comes with a new flag toplevel_mode which might be especially useful to test and debug CHR programs. It was highlighted in the version announcements as follows:

After suggestion by Falco Nogatz, it is now possible to run the toplevel in recursive mode such that global variables remain bound. Nice for teaching CHR. Not clear what the other use cases are. Use ?- set_prolog_flag(toplevel_mode, recursive). to enable this.

Some insights on the discussion, implementation and usage of the new flag can be found in the related GitHub issue. It can be used to have a persistent constraint store over multiple queries in the toplevel. This way it is possible to, e.g., use the classical gcd/1 constraint solver incrementally for computing the greatest common divisor of numbers given on by one:

?- set_prolog_flag(toplevel_mode, recursive).
true.
?- gcd(24).
gcd(24).
?- gcd(42).
gcd(6).
?- X = 3.
X = 3,
gcd(6).

As seen in the last query, the contents of the constraint store are printed by default on every query. So, for more advanced usage, it might become handy to use the recursive toplevel mode with CHR’s flag chr_toplevel_show_store set to false and explicitly call the meta-predicate chr_show_store/1.

As a PC-member I encourage submissions to

19th International Symposium on Practical Aspects of Declarative Languages (PADL 2017) Paris, France, 16th and 17th January 2017 http://bit.ly/PADL-2017

PADL 2017 welcomes new ideas and approaches pertaining to applications and implementation of declarative languages. PADL 2017 will be co-located with the Symposium on Principles of Programming Languages (POPL 2017), in Paris, France.