# 9 CHR: Constraint Handling Rules

This chapter is written by Tom Schrijvers, K.U. Leuven, and adjustments by Jan Wielemaker.

The CHR system of SWI-Prolog is the K.U.Leuven CHR system. The runtime environment is written by Christian Holzbaur and Tom Schrijvers while the compiler is written by Tom Schrijvers. Both are integrated with SWI-Prolog and licensed under compatible conditions with permission from the authors.

The main reference for the K.U.Leuven CHR system is:

- T. Schrijvers, and B. Demoen, The K.U.Leuven CHR System: Implementation and Application, First Workshop on Constraint Handling Rules: Selected Contributions (Frühwirth, T. and Meister, M., eds.), pp. 1--5, 2004.

On the K.U.Leuven CHR website (http://dtai.cs.kuleuven.be/CHR/) you can find more related papers, references and example programs.

## Section Index