Implementing Constraint Handling Rules as a Domain-Specific Language Embedded in Java

TL;DR

This paper presents a Java-embedded domain-specific language for implementing Constraint Handling Rules (CHR), enhancing integration, debugging, and development of constraint solvers in large-scale, dynamic cloud applications.

Contribution

It introduces a Java-based DSL for CHR, simplifying development, testing, and debugging of constraint solvers within mainstream programming environments.

Findings

Prototype supports transactional store behavior

Enables safe termination and debugging

Facilitates integration with Java applications

Abstract

Programming languages and techniques based on logic and constraints, such as the Constraint Handling Rules (CHR), can support many common programming tasks that can be expressed in the form of a search for feasible or optimal solutions. Developing new constraint solvers using CHR is especially interesting in configuration management for large scale, distributed and dynamic cloud applications, where dynamic configuration and component selection is an integral part of the programming environment. Writing CHR-style constraint solvers in a domain-specific language which is a subset of Java -- instead of using a separate language layer -- solves many integration, development cycle disruption, testing and debugging problems that discourage or make difficult the adoption of the CHR-based approach in the mainstream programming environments. Besides, the prototype implementation exposes a well-defined API that supports transactional store behavior, safe termination, and debugging via event notifications.