# Constraint Handling Rules - What Else?

## TL;DR

Constraint Handling Rules (CHR) is a versatile, declarative programming language with a strong theoretical foundation, efficient execution, and powerful analysis tools, extensively applied since 2000.

## Contribution

This paper provides an overview of CHR research and applications focusing on developments since 2000, highlighting its features and practical relevance.

## Key findings

- CHR has a solid semantic foundation in logic.
- It supports efficient sequential and parallel execution.
- CHR offers powerful analysis methods for program properties.

## Abstract

Constraint Handling Rules (CHR) is both an effective concurrent declarative constraint-based programming language and a versatile computational formalism. While conceptually simple, CHR is distinguished by a remarkable combination of desirable features: - semantic foundation in classical and linear logic, - effective and efficient sequential and parallel execution model - guaranteed properties like the anytime online algorithm properties - powerful analysis methods for deciding essential program properties. This overview of CHR research and applications is by no complete. It concentrates on the years since 2000. Up-to-date information on CHR can be found at the CHR web-site www.constraint-handling-rules.org, including the slides of the keynote talk associated with this article, an extensive bibliography, online demo versions and free downloads of the language.