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Research And Implemetation On Spatio-Temporal Query Processing And Optimization

Posted on:2007-06-19Degree:MasterType:Thesis
Country:ChinaCandidate:H XuFull Text:PDF
GTID:2178360242961957Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
Spatio-temporal database management system (STDBMS) is a kind of DBMS that can deal with both spatial and temporal data. In recent years, by deeply researching in wireless network and mobile computing and developing in interrelated technique, STDBMS has become an important branch of database technique.Spatio-temporal (ST) querying process is an indispensable part of STDBMS. The main task of ST query processing is how to process spatio-temporal data efficiently based on requirement of applications. Making use of the structure of ST indices, and applying distance metrics to decrease average disk access count is the most popular method in ST query processing.Modifying the classical distance metrics definition in nearest neighbor search, it's a beneficial attempt in querying process that research in combining nearest neighbor query with range query. Contrail system is a prototype of STDBMS which supports nearest neighbor query and range query on moving objects trajectories. Query processing in Contrail system identifies the spatial distance between target object and data objects to reduce the searching data space, it implements nearest neighbor query and range query via recursive algorithms.On the other hand, the strategy of ST query optimization can also affect the efficiency of ST query processing. Constructing an appropriate cost model has important effect on selecting a query plan. Existing cost model based on spatial indices can not accurately estimate the cost of ST query, a cost model based on ST indices which is constructed by computing the maximum spatial intervals intersecting with ST query can accurately estimate the number of disk accesses. Because the accuracy of selectivity estimation can directly affect choosing efficient query plan, computing the ratio between the area of region passed by ST query and that of the whole spatial universe in order to estimate the selectivity can guarantee higher accuracy.
Keywords/Search Tags:spatio-temporal database, nearest neighbor, distance metrics, cost model, selectivity estimation
PDF Full Text Request
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