We (my PhD student Edmund and me) have just submitted a paper with this title to Theory and Practice of Logic Programming. The paper complements our PPDP'08 paper on parallel Constraint Handling Rules execution. You can get the paper here.
Here's what the abstract says:
We introduce a systematic, concurrent execution scheme for Constraint Handling Rules (CHR) based on a previously proposed goal-based CHR semantics. We establish strong correspondence results to the abstract CHR semantics, thus guaranteeing that any answer in the concurrent, goal-based CHR semantics is reproducible in the abstract CHR semantics. Our work provides the foundation to obtain efficient, parallel CHR execution schemes.