CHR 2008

Fifth Workshop on Constraint Handling Rules

Hagenberg, Austria at the occasion of RTA 2008

July 14th


The Constraint Handling Rules (CHR) language has become a major declarative specification and implementation language for constraint reasoning algorithms and applications. Algorithms are often specified using inference rules, rewrite rules, sequents, proof rules or logical axioms that can be directly written in CHR.  Its clean semantics facilitates program design, analysis and transformation.  See the CHR website for more information.

Previous Workshops on Constraint Handling Rules were organized in May 2004 in Ulm (Germany), in October 2005 in Sitges (Spain) at ICLP, in July 2006 in Venice (Italy) at ICALP, and in September 2007 in Porto (Portgual) at ICLP.

Topics of Interest

The workshop calls for full papers and short papers describing ongoing work, on all aspects of CHR, including topics such as:

  • (Logical) Algorithms
  • Applications
  • Comparisons with Related Approaches
  • Constraint Solvers
  • Critical Assessment
  • Expressivity and Complexity
  • Implementations and Optimization
  • Language Extensions (Types, Modules)
  • Program Analysis
  • Program Transformation and Generation
  • Programming Environments (Debugging)
  • Programming Pearls
  • Retractable Constraints
  • Semantics
  • Programming Tools
  • Language Extensions (Debugging)

The call for papers can be found here.

Invited Talk

The workshop will feature an invited talk on "The CHR-Celf Connection" from Anders Schack-Nielsen and Carsten Schürmann.


Celf is a meta-language for specifying and implementing deductive and concurrent systems from areas, such as programming language theory, process algebras, and logics.  It is based on the concurrent logical framework CLF.  The Constraint Handling Rules (CHR) language is a major specification and implementation language for constraint-based algorithms.

In this invited talk, we give a tutorial-style introduction to Celf for the CHR programmer where we highlight some of Celf's features including the support of higher-order encodings, first-class execution traces, and a logically inspired proof search semantics. Furthermore we show where the semantics of the two languages coincide.

Accepted Papers

  • Beata Sarna-Starosta, Tom Schrijvers: Transformation-based Indexing Techniques for Constraint Handling Rules
  • Frank Raiser, Thom Frühwirth: Towards Term Rewriting Systems in Constraint Handling Rules
  • Paolo Pilozzi, Danny DeSchreye: Termination Analysis of Constraint Handling Rules
  • Edmund S.L. Lam, Martin Sulzmann: Finally, A Comparison Between Constraint Handling Rules and Join-Calculus
  • Remy Haemmerle, Hariolf Betz: Verification of Constraint Handling Rules using Linear Logic Phase Semantics
  • Peter Van Weert: A Tale of Histories
  • François Fages, Cleyton Mario de Oliveira Rodrigues, Thierry Martinez: Modular CHR with ask and tell
  • Marcos Aurelio, François Fages, Jacques Robin: Default Reasoning in CHRd
  • Beata Sarna-Starosta, David Zook, Emir Pasalic, Molham Aref: Relating Constraint Handling Rules to Datalog
  • Jon Sneyers, Thom Frühwirth: Generalized CHR Machines
  • Henning Christiansen: Prioritized Abduction with CHR


The workshop proceedings have been published as a RISC TR and are available here.

Program Committee

  • François Fages, INRIA Rocquencourt
  • Peter J. Stuckey, NICTA Victoria Laboratory
  • Jacques Robin, Universidade Federal de Pernambuco
  • Martin Sulzmann, National University of Singapore
  • Maurizio Gabbrielli, Universita di Bologna
  • Slim Abdennadher, German University in Cairo
  • Thom Frühwirth, Universität Ulm
  • Tom Schrijvers, Katholieke Universiteit Leuven
  • Armin Wolf, Fraunhofer FIRST, Berlin
  • Verónica Dahl, Simon Fraser University in Vancouver
  • Beata Sarna-Starosta, Michigan State University
  • Evelina Lamma, Università di Ferrara

Workshop Coordinators

Tom Schrijvers
Department of Computer Science

Thom Frühwirth
Faculty of Engineering and Computer Science
University Ulm

Frank Raiser
Faculty of Engineering and Computer Science
University Ulm