| Popis: |
Caching legitimate districts of spatial queries at mobile clients is effective in reducing the number of queries submitted by wireless clients and query burden on the server although, wireless purchasers suffer from longer waiting time for the server to compute valid districts. We propose in this paper a proxy-based approach to continuous nearest-neighbor (NN) and window queries. The proxy conceives approximated valid regions (EVRs) for wireless purchasers by exploiting spatial and temporal locality of spatial queries. For NN queries, we develop two new algorithms to accelerate EVR development, premier the proxy to build effective EVRs even when the cache dimension little. On the other hand, we suggest to comprise the EVRs of window queries in the pattern of vectors, called approximated window vectors (EWVs), to accomplish larger approximated legitimate districts. The spatial objects are located with a given window by using the hilbert curve-based distributed index for window queries in the wireless broadcast system. Moreover, to quickly answer window queries, for utilizing the distributed spatial index, space filling curves particularly, Hilbert curves extremely used to maintain spatial locality of multidimensional data in wide variety of application. Here we see the properties of Hilbert curve, window query process is corresponding to the order without the need to decode all the points inside the window to the Hilbert order. |
