Query in Road Network

There are two typical kinds of queries in road network: precise query and aggregate query. Nearest neighbor query (NN) and continuous nearest neighbor query (CNN) belong to precise queries which would get exact location in road network and are used widely in ITS. The non-Euclidean property of road network is the most significant problem in these queries. Cyclic Optimal Multi-step Algorithm divides the temporal query into two stages: filter and refinement. The algorithm uses non-Euclidean semantic distance as filter condition to generate candidates. Followed by refinement step, the filter conditions are constantly revised and the above process is iterated to enhance the retrieval efficiency by using the spatial index created in Euclidean space.