最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
XML Schema 参考手册 完整 XML Schema 参考手册 The group element is used to define the group of elements used in a complex type definition. 父元素： Schema, choice, sequence, complexType, restriction (both simpleContent and complexContent), extension (both simpleContent and complexContent) (? The symbol is declared in the group element, which can appear zero or once. ) Attribute Description Id Optional. Specifies the unique ID of the element. Name Optional. Specifies the name of the group. The name must be a colon-free name (NCName) defined in the XML namespace specification. This attribute is used only if the schema element is the parent of the group element. In this case, group is the model group used by the complexType, choice, and sequence elements. The name property and the ref property cannot appear at the same time. Ref Optional. Reference the name of another group. The ref value must be QName. Ref can contain namespace prefixes. The name property and the ref property cannot appear at the same time. MaxOccurs Optional. Specifies the maximum number of times an group element can appear in the parent element. The value can be an integer greater than or equal to zero. If you do not want to set any limit on the maximum number of times, use the string “unbounded”. The default value is 1. MinOccurs Optional. Specifies the minimum number of times an group element can appear in the parent element. The value can be an integer greater than or equal to zero. The default value is 1. Any attributes Optional. Specifies any other attributes with the non-schema namespace. The following example defines a group that contains a sequence of four elements and uses this group element in a complex type definition: XML Schema 参考手册 完整 XML Schema 参考手册 Definition and usage ¶
Element information ¶
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Example 1 ¶