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 restriction element defines constraints on simpleType, simpleContent, or complexContent definitions. 父元素： SimpleType, simpleContent, complexContent (? The symbol declares that the element can appear zero or once in the restriction element. ) Attribute Description Id Optional. Specifies the unique ID of the element. Base Necessary. Specifies the name of the built-in data type, simpleType, or complexType element defined in the schema (or other schema indicated by the specified namespace). Any attributes Optional. Specifies any other attributes with the non-schema namespace. The following example defines an element named “age” with constraints. The value of age cannot be less than 0 or greater than 100: This example defines an element named “initials”. The “initials” element is a simple type with constraints. Acceptable values are three uppercase or lowercase letters from a to z: This example defines an element named “password”. The “password” element is a simple type with constraints. The value must be at least 5 characters and up to 8 characters: This example shows a complex type definition that uses constraints. The complex type “Chinese_customer” is derived from a normal customer complex type, and the fixed value of its country element is “China”: XML Schema 参考手册 完整 XML Schema 参考手册 Definition and usage ¶
Element information ¶
Grammar ¶
Example 1 ¶
<xs:element name="age"> <xs:simpleType> <xs:restriction base="xs:integer"> <xs:minInclusive value="0"/> <xs:maxInclusive value="100"/> xs:restriction> xs:simpleType> xs:element>
Example 2 ¶
<xs:element name="initials"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:pattern value="[a-zA-Z][a-zA-Z][a-zA-Z]"/> xs:restriction> xs:simpleType> xs:element>
Example 3 ¶
<xs:element name="password"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:minLength value="5"/> <xs:maxLength value="8"/> xs:restriction> xs:simpleType> xs:element>
Example 4 ¶
<xs:complexType name="customer"> <xs:sequence> <xs:element name="firstname" type="xs:string"/> <xs:element name="lastname" type="xs:string"/> <xs:element name="country" type="xs:string"/> xs:sequence> xs:complexType> <xs:complexType name="Norwegian_customer"> <xs:complexContent> <xs:restriction base="customer"> <xs:sequence> <xs:element name="firstname" type="xs:string"/> <xs:element name="lastname" type="xs:string"/> <xs:element name="country" type="xs:string" fixed="Norway"/> xs:sequence> xs:restriction> xs:complexContent> xs:complexType>