GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended v...GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended versions） are not suitable for direct querying and updating of GML documents. Even the effective approaches working well with XML could not guarantee good results when applied to GML documents. Although XQuery is a powerful standard query language for XML, it is not proposed for querying spatial features, which constitute the most important components in GML documents. We propose GQL, a query language specification to support spatial queries over GML documents by extending XQuery. The data model, algebra, and formal semantics as well as various spatial Junctions and operations of GQL are presented in detail.展开更多
With rapid development of urbanization and regional interaction and interdependence, regional urban agglomeration planning becomes more and more important in China, in order to promote integrated development of variou...With rapid development of urbanization and regional interaction and interdependence, regional urban agglomeration planning becomes more and more important in China, in order to promote integrated development of various cities with close interrelationship. However, it is still arguable academically on how to define the boundary or which cities to be included for the urban agglomeration of a region. This paper aims to shed lights on how to identify urban spheres of influence scientifically by introducing field modeling method and by practicing a case study on 168 cities in Central China. In our field modeling method, the influence intensities of cities were measured by a compre-ensive index and urban spheres of influence were represented spatially by field intensity. Then, their classification and spatial distribution characteristics of study area in 2007 were identified and explored by using GIS and statistical methods. The result showed that： 1） Wuhan is the absolute dominant city in Central China; 2） the provincial capital cities dominate their own provinces and there are no other lower grade agglomeration centers; and 3） the basic types of organization form of urban sphere of influence are single-polar type, agglomeration type, close-related group type and loose-related group type.展开更多
基金Funded by the Youth Chengguang Project of Science and Technology of Wuhan City of China(No.20045006071-16)
文摘GML is becoming the de facto standard for electronic data exchange among the applications of Web and distributed geographic information systems. However, the conventional query languages （e. g. SQL and its extended versions） are not suitable for direct querying and updating of GML documents. Even the effective approaches working well with XML could not guarantee good results when applied to GML documents. Although XQuery is a powerful standard query language for XML, it is not proposed for querying spatial features, which constitute the most important components in GML documents. We propose GQL, a query language specification to support spatial queries over GML documents by extending XQuery. The data model, algebra, and formal semantics as well as various spatial Junctions and operations of GQL are presented in detail.
基金Under the auspices of National Natural Science Foundation of China (No. 40971102)Knowledge Innovation Programs of Chinese Academy of Sciences (No. KZCX2-YW-322)Special Grant for Postgraduates' Scientific Innovation and Social Practice in 2008
文摘With rapid development of urbanization and regional interaction and interdependence, regional urban agglomeration planning becomes more and more important in China, in order to promote integrated development of various cities with close interrelationship. However, it is still arguable academically on how to define the boundary or which cities to be included for the urban agglomeration of a region. This paper aims to shed lights on how to identify urban spheres of influence scientifically by introducing field modeling method and by practicing a case study on 168 cities in Central China. In our field modeling method, the influence intensities of cities were measured by a compre-ensive index and urban spheres of influence were represented spatially by field intensity. Then, their classification and spatial distribution characteristics of study area in 2007 were identified and explored by using GIS and statistical methods. The result showed that： 1） Wuhan is the absolute dominant city in Central China; 2） the provincial capital cities dominate their own provinces and there are no other lower grade agglomeration centers; and 3） the basic types of organization form of urban sphere of influence are single-polar type, agglomeration type, close-related group type and loose-related group type.
