Wireless sensor networks have been widely used for environment monitoring and event surveillance. In recent years, the skyline query, as an important operator for multiple-criteria decision making, has received much attention because of its many real-world applications. In this paper, we propose a new filter-based method, called SKYFILTER, for skyline query processing. Our method provides an enhanced efficiency by reduction of the total wireless communication between sensor nodes. In addition, the proposed method also provides a better performance than other existing methods with respect to the computational efficiency of skyline computation in sensor nodes. In this paper, we first present a new multiple filter-based technique to reduce wireless communication. Then, we provide a new merge sort-based algorithm for efficient skyline computation in sensor nodes. We show through performance experiments and algorithm analysis that the proposed method generally provides a better performance than other existing methods in terms of the wireless communication cost and computational efficiency.

Histograms have been widely used for fast estimation of query result sizes in query optimization. In this paper, we propose a new histogram method, called the Skew-Tolerant Histogram (STHistogram) for two or three dimensional geographic data objects that are used in many real-world applications in practice. The proposed method provides a significantly enhanced accuracy in a robust manner even for the data set that has a highly skewed distribution. Our method detects hotspots present in various parts of a data set and exploits them in organizing histogram buckets. For this purpose, we first define the concept of a hotspot, and provide an algorithm that efficiently extracts hotspots from the given data set. Then, we present our histogram construction method that utilizes hotspot information. We also describe how to estimate query result sizes by using the proposed histogram. We show through extensive performance experiments that the proposed method provides better performance than other existing methods.