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.

Klick here for more information on our research.


Frühwirth, Thom; Abdennadher, Slim
Essentials of Constraint Programming
Herausgeber: Springer-Verlag
Februar 2003
Abdennadher, Slim; Frühwirth, Thom
Integration and Optimization of Rule-based Constraint Solvers
International Symposium on Logic-based Program Synthesis and Transformation (LOPSTR'03)
Frühwirth, Thom; Holzbaur, Christian
Source-to-Source Transformation for a Class of Expressive Rules
In Buccafurri, F., Editor, Joint Conference on Declarative Programming APPIA-GULP-PRODE 2003 (AGP 2003), Seite 386-397
In Buccafurri, F., Editor


Frühwirth, Thom
As Time Goes By II: More Automatic Complexity Analysis of Concurrent Rule Programs
In Di Pierro, A. and Wiklicky, H., Editor, Quantitative Aspects of Programming Laguages, QAPL'01Band59ausElectronic Notes in Theoretical Computer Science, Seite 185-206
In Di Pierro, A. and Wiklicky, H., Editor
November 2002
Frühwirth, Thom; Di Pierro, A.; Wiklicky, H.
Probabilistic Constraint Handling Rules
In Comini, M. and Falaschi, M., Editor, 11th International Workshop on Functional and (Constraint) Logic Programming, WFLP 2002Band76ausElectronic Notes in Theoretical Computer Science, Seite 115-130
In Comini, M. and Falaschi, M., Editor
November 2002