The world has seen rapid growth in GPS-based devices and location aware systems in the past decade or so which has contributed a lot to location based services (LBSs) that deliver services based on the geographic location. One of the popular LBS application is continuous k reverse nearest neighbors (RkNN) in directed road network, where a road segment can have a particular orientation. A RkNN query returns a set of data objects that take query point as their nearest neighbor. A challenging task in this type of query is to keep the result fresh as the query moves freely in the road network. This is a significant task as evaluating a query at timestamps will create a significant burden on the server and communication costs will be much higher.
In order to address this problem, we propose an efficient approach for computing the safe region and safe exit points for moving RkNN query in a directed road network. A safe region of query is a location in the road network where the answer objects of the query remains unchanged. A safe exit point is a point where safe region and non-safe region meet and as long as the query has not passed the safe exit point, it is guaranteed that the query result is valid hence no communication is required between the server and the client. In contrast, previous RkNN algorithms only work for undirected road networks or Euclidian space.
