CHR Research Group

Constraint Handling Rules (CHR) is a concurrent committed-choice constraint logic programming language consisting of guarded rules that transform multi-sets of atomic formulas (constraints) until exhaustion. It was designed by Thom Fruehwirth in 1991. CHR can embed many rule-based formalisms and systems, and it can describe algorithms in a compact declarative way without compromising efficiency. The clean semantics of CHR ensures that several desirable properties hold for CHR programs and also facilitates sophisticated program analysis. CHR libraries exist for Prolog, Haskell, Java, Javascript, Python and C. CHR is also available online for experimentation with many example programs. More than 250 academic and industrial projects worldwide use CHR, and about 2500 research papers reference it.

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Gall, Daniel; Frühwirth, Thom
A Refined Operational Semantics for ACT-R
ACM 17th International Symposium on Principles and Practice of Declarative Programming (PPDP 2015), Siena, Italy
Juli 2015
Sharaf, Nada; Abdennadher, Slim; Frühwirth, Thom
DiagrammaticCHR: A Diagrammatic Representation of CHR Program
19th International Conference Information Visualisation (iV2015)
Herausgeber: IEEE Digital Library
Juli 2015
Dahl, Veronica; Tessaris, Sergio; Frühwirth, Thom
Imperfect Querying through Womb Grammars plus Ontologies
Workshop Ontologies and Logic Programming for Query Answering (ONTOLP'15) at IJCAI-2015, Buenos Aires
Juli 2015
Gall, Daniel; Frühwirth, Thom
An Adaptable Implementation of ACT-R with Refraction in Constraint Handling Rules
13th International Conference on Cognitive Modeling (ICCM), Groningen
April 2015


Sharaf, Nada; Abdennadher, Slim; Frühwirth, Thom
A Visualization Tool for Constraint Handling Rules
24th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2014), Canterbury, UK
September 2014
Saad, Aya; Frühwirth, Thom; Gervet, Carmen
The P-Box CDF-Intervals: A Reliable Constraint Reasoning with Quantifiable Information
, Selected Papers of the 30th International Conference on Logic Programming (ICLP 2014)Band14(4-5), Seite 461-475
Herausgeber: Cambridge University Press
Juli 2014
Gall, Daniel; Frühwirth, Thom
Exchanging Conflict Resolution in an Adaptable Implementation of ACT-R
, Selected Papers of the 30th International Conference on Logic Programming (ICLP 2014)Band14(4-5), Seite 525-538
Herausgeber: Cambridge University Press
Juli 2014
Nogatz, Falco; Frühwirth, Thom
From XML Schema to JSON Schema: Translation with CHR
11th Workshop on Constraint Handling Rules (CHR 2014), Vienna
Juli 2014
Wielemaker, Jan; Frühwirth, Thom; Koninck, Leslie De; Triska, Markus; Uneson, Marcus
SWI Prolog Reference Manual 7.1
Mai 2014
Herausgeber: BOD


Sneyers, Jon; Schreye, Daniel De; Frühwirth, Thom
Probabilistic Legal Reasoning in CHRiSM
, Selected Papers of the 29th International Conference on Logic Programming (ICLP 2013)Band13, 4-5-Online-Supplement
Herausgeber: Cambridge University Press
August 2013