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1、XML的作用

  XML 被设计用来传输和存储数据。所以XML 是不作为的。

2、简单的描述 

  XML 文档形成一种树结构。

  XML 文档必须包含 根元素。该元素是所有其他元素的父元素。XML 文档中的元素形成了一棵文档树。这棵树从根部开始,并扩展到树的最底端。所有元素均可拥有子元素:
  <root>    <child>      <subchild>.....</subchild>    </child>  </root>

   父、子以及同胞等术语用于描述元素之间的关系。父元素拥有子元素。相同层级上的子元素成为同胞(兄弟或姐妹)。所有元素均可拥有文本内容和属性(类似 HTML 中)。

3、语法规则

  所有 XML 元素都须有关闭标签

 XML 标签对大小写敏感

 XML 必须正确地嵌套

 XML 文档必须有根元素

 XML 的属性值须加引号

 实体引用

261206085084e2d15546437b5c84c175 > 大于
& & 和号
' ' 单引号
" " 引号
 

 

 

 

 

 XML 中的注释

 在 XML 中编写注释的语法与 HTML 的语法很相似:
<!-- This is a comment --> 

 在 XML 中,空格会被保留

  在 XML 中,文档中的空格不会被删节。

 XML 以 LF 存储换行

 在 Windows 应用程序中,换行通常以一对字符来存储:回车符 (CR) 和换行符 (LF)。这对字符与打字机设置新行的动作有相似之处。在 Unix 应用程序中,新行以 LF 字符存储。而 Macintosh 应用程序使用 CR 来存储新行。

 

4、实例

  上图表示下面的 XML 中的一本书:

 1 <bookstore> 2 <book category="COOKING"> 3   <title lang="en">Everyday Italian</title>  4   <author>Giada De Laurentiis</author>  5   <year>2005</year>  6   <price>30.00</price>  7 </book> 8 <book category="CHILDREN"> 9   <title lang="en">Harry Potter</title> 10   <author>J K. Rowling</author> 11   <year>2005</year> 12   <price>29.99</price> 13 </book>14 <book category="WEB">15   <title lang="en">Learning XML</title> 16   <author>Erik T. Ray</author> 17   <year>2003</year> 18   <price>39.95</price> 19 </book>20 </bookstore>

 

  例子中的根元素是 。文档中的所有 元素都被包含在 中。

   元素有 4 个子元素:、、<year>、<price>。</price></year>

 

总结:1、这种可扩展的标记语言主要用来用来传输和存储数据,XML自己不作为,只有使用程序语言或者XML工具才能传送、接收和显示出这个文档。

   2、语法规则:根元素,标签成对嵌套出现,区分大小写,属性必须加引号,5中特殊字符的实体引用,空格会被呈现

   3、节点和元素的关系留在下一篇中讲解

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