tailieunhanh - Decoupling Partitioning and Grouping: Overcoming Shortcomings of Spatial Indexing with Bucketing

Society can contribute to the establishment and growth of car-sharing by supporting it in various ways. This in turn can benefit society by reducing the negative effects of car traffic on the environment and by improving urban environments generally. The support provided should not be of economic character, since most car-sharing organizations today are on firm economic footing, having achieved this on their own. The Swedish National Road Administration's responsibilities concerning the expanded use of car-sharing involve primarily spreading information about car-sharing and removing hindrances to its growth. The major responsibility for providing support for individual car- sharing organizations lies. | CAR-TR-989 CS-TR-4523 UMIACS 2003-91 August 2003 Decoupling Partitioning and Grouping Overcoming Shortcomings of Spatial Indexing with Bucketing Hanan Samet Computer Science Department Center for Automation Research Institute for Advanced Computer Studies University of Maryland College Park Maryland 20742 Abstract The principle of decoupling the partitioning and grouping processes that form the basis of most spatial indexing methods that use tree directories of buckets is explored. The decoupling is designed to overcome the following drawbacks of traditional solutions 1. Multiple postings in disjoint space decomposition methods that lead to balanced trees such as the hB-tree where a node split in the event of node overflow may be such that one of the children of the node that was split becomes a child of both of the nodes resulting from the split. 2. Multiple coverage and nondisjointness of methods based on object hierarchies such as the R-tree which lead to nonunique search paths. 3. Directory nodes with similarly-shaped hyper-rectangle bounding boxes with minimum occupancy in disjoint space decomposition methods such as those based on quadtrees and k-d trees that make use of regular decomposition. The first two drawbacks are shown to be overcome by the BV-tree where as a result of decoupling the partitioning and grouping processes the union of the regions associated with the nodes at a given level of the directory does not necessarily contain all of the data points although all searches take the same amount of time. The BV-tree is not plagued by the third drawback. The third drawback is shown to be overcome by the PK-tree where the grouping process is based on ensuring that every node has at least k objects or blocks. The PK-tree is not plagued by the first two drawbacks as they are inapplicable to it. In both cases the downside of decoupling the partitioning and grouping The support of the National Science Foundation under Grants EIA-99-00268 IIS-00-86162 and .

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