# COMPUTER SCIENCE QATAR TECHNICAL REPORT ABSTRACTS

**Source**: http://reports-archive.adm.cs.cmu.edu/anon/qatar/abstracts/14-122.html
**Parent**: http://reports-archive.adm.cs.cmu.edu/qatar.html

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|  | **CMU-CS-QTR-122**  Computer Science Qatar  School of Computer Science, Carnegie Mellon University ---   **CMU-CS-QTR-122** Edmund S.L. Lam, Iliano Cervesato June 2014 [CMU-CS-QTR-122.pdf](http://reports-archive.adm.cs.cmu.edu/anon/qatar/CMU-CS-QTR-122.pdf) *Also appears as Computer Science Department  Technical Report CMU-CS-14-119*   **Keywords:** Multiset Rewriting, Logic Programming, Comprehension, Compilation   We extend the rule-based, multiset rewriting language *CHR* with multiset comprehension patterns. Multiset comprehension provides the programmer with the ability to write multiset rewriting rules that can match a variable number of entities in the state. This enables implementing algorithms that coordinate large amounts of data or require aggregate operations in a declarative way, and results in code that is more concise and readable than with pure *CHR*. We call this extension *CHRcp*. In this paper, we formalize the operational semantics of *CHRcp* and define a low-level optimizing compilation scheme based on join ordering for the efficient execution of programs. We provide preliminary empirical results that demonstrate the scalability and effectiveness of this approach. 44 pages |
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