Changxiu Cheng

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Finding a balance between data redundancy and manipulation efficiency can sometimes be problematic when building multi-scale spatial databases (MSDBs). In order to render MSDBs real-timely, coarser representations with fewer vertices should be invoked once the response time exceeds the tolerable limitation. Of course, this would result in faster response(More)
Current database with numerous users requires access control. It is also needed in spatial database systems that keep both spatial attribute and non-spatial attribute safe. The query rewriting technology in spatial database is discussed in this paper. First the operations for merging authorization policies are discussed. By classifying the subjects and(More)
The generation algorithm of permutation based on sorting makes the Series of permutations have some special features. The features guide the next generation under the current permutation, so the algorithm can effectively control the process of generating permutation. And the extended permutation generation algorithm based on sorting can meet some special(More)
How to process massive historic natural disasters events is a great challenge to recognize patterns. And more and more scientific research data provides a new source of nature disasters. In this study, the biclustering method is used to categorize the scientists concerned natural disasters and historic events. Cartograms, one kind of transformed maps, are(More)