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<p><b>Abstract</b>—This paper introduces techniques for reducing data dissemination costs of query subscriptions in a multicast environment. The reduction is achieved by merging queries with overlapping, but not necessarily equal, answers. The paper formalizes the query-merging problem and introduces a general framework and cost model for evaluating merging. We prove that the problem is NP-hard and propose exhaustive algorithms and three heuristic algorithms: The Pair Merging Algorithm, the Directed Search Algorithm, and the Clustering Algorithm. We develop a simulator, which uses geographical queries as a representative example for evaluating the different heuristics and show that the performance of our heuristics is close to optimal.</p>
Query processing, data dissemination, query merging, query subscriptions, query result multicast, geographical queries.

H. Garcia-Molina, A. Crespo and O. Buyukkokten, "Query Merging: Improving Query Subscription Processing in a Multicast Environment," in IEEE Transactions on Knowledge & Data Engineering, vol. 15, no. , pp. 174-191, 2003.
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