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A Safe-Region Approach to a Moving <i>k</i> -RNN Queries in a Directed Road Network
Zeberga, Kamil,Jin, Rize,Cho, Hyung-Ju,Chung, Tae-Sun World Scientific Publishing Company 2017 Journal of circuits, systems, and computers Vol.26 No.5
<P>In road networks, <TEX>$ k$</TEX>-range nearest neighbor (<TEX>$ k$</TEX>-RNN) queries locate the <TEX>$ k$</TEX>-closest neighbors for every point on the road segments, within a given query region defined by the user, based on the network distance. This is an important task because the user's location information may be inaccurate; furthermore, users may be unwilling to reveal their exact location for privacy reasons. Therefore, under this type of specific situation, the server returns candidate objects for every point on the road segments and the client evaluates and chooses exact <TEX>$ k$</TEX> nearest objects from the candidate objects. Evaluating the query results at each timestamp to keep the freshness of the query answer, while the query object is moving, will create significant computation burden for the client. We therefore propose an efficient approach called a safe-region-based approach (SRA) for computing a safe segment region and the safe exit points of a moving nearest neighbor (NN) query in a road network. SRA avoids evaluation of candidate answers returned by the location-based server since it will have high computation cost in the query side. Additionally, we applied SRA for a directed road network, where each road network has a particular orientation and the network distances are not symmetric. Our experimental results demonstrate that SRA significantly outperforms a conventional solution in terms of both computational and communication costs.</P>