Constraint Handling Rules with Multiset Comprehension Patterns

TL;DR

This paper introduces an extension to the CHR programming language, called CHR^cp, which incorporates multiset comprehension patterns to enhance expressiveness for data coordination and aggregation tasks.

Contribution

The paper presents CHR^cp, a novel extension to CHR that allows multiset rewriting with comprehension patterns, along with its formal semantics and soundness proof.

Findings

Formal semantics of CHR^cp provided

Soundness of operational semantics established

Enhanced expressiveness for data aggregation demonstrated

Abstract

CHR is a declarative, concurrent and committed choice rule-based constraint programming language. We extend CHR with multiset comprehension patterns, providing the programmer with the ability to write multiset rewriting rules that can match a variable number of constraints in the store. This enables writing more readable, concise and declarative code for algorithms that coordinate large amounts of data or require aggregate operations. We call this extension $\mathit{CHR}^\mathit{cp}$. We give a high-level abstract semantics of $\mathit{CHR}^\mathit{cp}$, followed by a lower-level operational semantics. We then show the soundness of this operational semantics with respect to the abstract semantics.