Spatial join optimization of web feature services based on early filtering estimation
Author(s): LAN Gui-wen, CHEN Qi, CHEN Tian-wei
Pages: 310-313
Year: 2016 Issue: 2
Journal: Journal of GuiLin University of Technology
Keyword: web feature service; spatial join; filter ratio; query optimization;
Abstract: The OpenGIS Web Feature Service (WFS)Interface Standard provides an interface allowing requests and updates for geographical features across the web by the HTTP protocol.In such a web-service-oriented envi-ronment,an issued query may invovle two or more spatial datasets that are provided by different services at dif-ferent sites.The processes of generating GML document in the WFS server,transmitting it to and parsing it at the client site,are very time-consuming,which causes a bottleneck to application of WFSs for distributed spatial data integration.This paper examines the query optimization strategy of spatial joins between OGC-compliant WFSs,based on the methods of spatial semi-join and partition based spatial-merge join.To avoid blindness of spatial semi-join operations of sub-areas,an improved strategy is proposed in this paper.In early phase the fil-tering ratios of spatial semi-joins for all the sub-areas are estimated and used to generate execution plans of spa-tial semi-join operations.The experimental result illustrates that compared with the previous methods,the pro-posed strategy can improve the performance of spatial joins between two WFSs.
Pages: 310-313
Year: 2016 Issue: 2
Journal: Journal of GuiLin University of Technology
Keyword: web feature service; spatial join; filter ratio; query optimization;
Abstract: The OpenGIS Web Feature Service (WFS)Interface Standard provides an interface allowing requests and updates for geographical features across the web by the HTTP protocol.In such a web-service-oriented envi-ronment,an issued query may invovle two or more spatial datasets that are provided by different services at dif-ferent sites.The processes of generating GML document in the WFS server,transmitting it to and parsing it at the client site,are very time-consuming,which causes a bottleneck to application of WFSs for distributed spatial data integration.This paper examines the query optimization strategy of spatial joins between OGC-compliant WFSs,based on the methods of spatial semi-join and partition based spatial-merge join.To avoid blindness of spatial semi-join operations of sub-areas,an improved strategy is proposed in this paper.In early phase the fil-tering ratios of spatial semi-joins for all the sub-areas are estimated and used to generate execution plans of spa-tial semi-join operations.The experimental result illustrates that compared with the previous methods,the pro-posed strategy can improve the performance of spatial joins between two WFSs.
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