Communication-efficient preference top-k monitoring queries via subscriptions

With the increase of data generation in distributed fashions such as peer-to-peer systems and sensor networks, top-k query processing which returns only a small set of data that satisfies many users' preferences, becomes a substantial issue. When data are periodically updated in each epoch e.g., weather information, without any techniques, a naive solution is to aggregate all data and their updates to ensure the correctness of final answers, however, it is too costly in terms of data transfer especially for data aggregator nodes. In this paper, we propose a top-k monitoring query processing method in 2-tier distributed systems based on a publish-subscribe scheme. A set of top-k subscriptions specifying summary scope of users' interests is informed to aggregators to limit the number of transferred data records for each epoch. In addition, instead of issuing subscriptions of all queries, our method identifies a small set of minimal subscriptions resulting in lower communication overhead. Our experiments show that our technique is efficient and outperforms other comparative reactive methods.