In a DTD, elements are declared with an ELEMENT declaration.

Declaring Elements

In a DTD, XML elements are declared with an element declaration with the following syntax:

<!ELEMENT element-name category>

or

<!ELEMENT element-name (element-content)>

Empty Elements

Empty elements are declared with the category keyword EMPTY:

<!ELEMENT element-name EMPTY>

Example:

<!ELEMENT br EMPTY>

XML example:

<br />
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE br [

<!ELEMENT br EMPTY>

]>

<br/>

Elements with Parsed Character Data

Elements with only parsed character data are declared with #PCDATA inside

<!ELEMENT element-name (#PCDATA)>

Example:

<!ELEMENT from (#PCDATA)>

Elements with any Contents

Elements declared with the category keyword ANY, can contain any combination of parsable data:

<!ELEMENT element-name ANY>

Example:

<!ELEMENT note ANY>
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE content [

<!ELEMENT content (any+)>

<!ELEMENT any ANY>

]>

<content>

    <any></any>

    <any>

        <any></any>

    </any>

    <any>&lt;</any>

</content>

Elements with Children (sequences)

Elements with one or more children are declared with the name of the children elements inside parentheses:

<!ELEMENT element-name (child1)>

or

<!ELEMENT element-name (child1,child2,...)>

Example:

<!ELEMENT note (to,from,heading,body)>

When children are declared in a sequence separated by commas, the children must appear in the same sequence in the document. In a full declaration, the children must also be declared, and the children can also have children. The full declaration of the "note" element is:

<!ELEMENT note (to,from,heading,body)>

<!ELEMENT to (#PCDATA)>

<!ELEMENT from (#PCDATA)>

<!ELEMENT heading (#PCDATA)>

<!ELEMENT body (#PCDATA)>

Declaring Only One Occurrence of an Element

<!ELEMENT element-name (child-name)>

Example:

<!ELEMENT note (message)>

The example above declares that the child element "message" must occur once, and only once inside the "note" element.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note [

<!ELEMENT note (message)>

<!ELEMENT message (#PCDATA)>

]>

<note>

    <message></message>

</note>

Declaring Minimum One Occurrence of an Element

<!ELEMENT element-name (child-name+)>

Example:

<!ELEMENT note (message+)>

The + sign in the example above declares that the child element "message" must occur one or more times inside the "note" element.

Declaring Zero or More Occurrences of an Element

<!ELEMENT element-name (child-name*)>

Example:

<!ELEMENT note (message*)>

The * sign in the example above declares that the child element "message" can occur zero or more times inside the "note" element.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note [

<!ELEMENT note (message*)>

<!ELEMENT message (#PCDATA)>

]>

<note>

</note>

Declaring Zero or One Occurrences of an Element

<!ELEMENT element-name (child-name?)>

Example:

<!ELEMENT note (message?)>
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note [

<!ELEMENT note (message?)>

<!ELEMENT message (#PCDATA)>

]>

<note>

<message></message>

</note>

The ? sign in the example above declares that the child element "message" can occur zero or one time inside the "note" element.

Declaring either/or Content

Example:

<!ELEMENT note (to,from,header,(message|body))>

The example above declares that the "note" element must contain a "to" element, a "from" element, a "header" element, and either a "message" or a "body" element.

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note [

<!ELEMENT note (to,from,header,(message|body))>

<!ELEMENT to (#PCDATA)>

<!ELEMENT from (#PCDATA)>

<!ELEMENT header (#PCDATA)>

<!ELEMENT message (#PCDATA)>

<!ELEMENT body (#PCDATA)>

]>

<note>

    <to></to>

    <from></from>

    <header></header>

    <body></body>

</note>

Declaring Mixed Content

Example:

<!ELEMENT note (#PCDATA|to|from|header|message)*>
<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note [

<!ELEMENT note (#PCDATA|to|from|header|message)*>

<!ELEMENT to (#PCDATA)>

<!ELEMENT from (#PCDATA)>

<!ELEMENT header (#PCDATA)>

<!ELEMENT message (#PCDATA)>

<!ELEMENT body (#PCDATA)>

]>

<note>

    <to></to>

</note>

The example above declares that the "note" element can contain zero or more occurrences of parsed character data, "to", "from", "header", or "message" elements.

DTD - Elements的更多相关文章

  1. How to read the HTML DTD

    Contents How to read the HTML DTD 1. DTD Comments 2. Parameter Entity definitions 3. Element declara ...

  2. DTD - XML Building Blocks

    The main building blocks of both XML and HTML documents are elements. The Building Blocks of XML Doc ...

  3. Introduction to DTD

    A Document Type Definition (DTD) defines the legal building blocks of an XML document. It defines th ...

  4. DTD Tutorial

    The purpose of a DTD (Document Type Definition) is to define the legal building blocks of an XML doc ...

  5. 无废话XML--XML约束（DTD）

    基本术语     一.序言Prolog:包括XML声明(XML Declaration)和文档类型声明(Document Type Declaration).     二.良构(well-formed ...

  6. XML概念定义以及如何定义xml文件编写约束条件java解析xml DTD XML Schema JAXP java xml解析 dom4j 解析 xpath dom sax

    本文主要涉及:xml概念描述,xml的约束文件,dtd,xsd文件的定义使用,如何在xml中引用xsd文件,如何使用java解析xml,解析xml方式dom sax,dom4j解析xml文件 XML来 ...

  7. XML与DTD

    什么是XML XML个称为Extensible Markup Language,意思是可扩展的标记语言. 应用常见 配置文件 <?xml version="1.0" enco ...

  8. DTD -- XML验证

    DTD(文档类型定义)的作用是定义 XML 文档的合法构建模块. DTD 可被成行地声明于 XML 文档中,也可作为一个外部引用. DTD简介 内部的 DOCTYPE 声明 假如 DTD 被包含在您的 ...

  9. js81:Image对象，几张图像缓存完之后动画显示，form.elements[],document.images[]

    原文发布时间为:2008-11-09 -- 来源于本人的百度文章 [由搬家工具导入] <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Tran ...

随机推荐

  1. Win7 默认hosts文件

    # Copyright (c) 1993-2009 Microsoft Corp. # # This is a sample HOSTS file used by Microsoft TCP/IP f ...

  2. 每个QWidget都有contentsMargins函数，善用QMargins

    m_pSearchLineEdit = new QLineEdit(); QPushButton *pSearchButton = new QPushButton(this); pSearchButt ...

  3. SQL Server 2012 连接到数据库引擎

    第 1 课:连接到数据库引擎 https://msdn.microsoft.com/zh-cn/library/ms345332(v=sql.110).aspx   本课将介绍主要的工具以及如何连接并 ...

  4. node.js EventEmitter发送和接收事件

    EventEmitter是nodejs核心的一部分.很多nodejs对象继承自EventEmitter,用来处理事件,及回调.api文档地址: http://nodejs.org/api/events ...

  5. poj 1442 Black Box（堆 优先队列）

    题目:http://poj.org/problem?id=1442 题意:n,m,分别是a数组,u数组的个数,u[i]w为几,就加到a几,然后输出第i 小的 刚开始用了一个小顶堆,超时,后来看了看别人 ...

  6. 生产环境上shell的解读

    一直以来对shell都不是很熟悉,只停留在基本的linux上操作上,这周因为定位问题接触到了生产环境上的脚本,因此作为引子学习一下.很多命令只是点到,等真正需要独立完成的时候再去学习. #!/bin/ ...

  7. FormsAuthentication 登录兼容 IE11 保存cookie

    现象:使用FormsAuthentication进行登录验证,在IE11客户端无法保存cookie 解决方法:在web.config中的forms中增加cookieless="UseCook ...

  8. BZOJ1954: Pku3764 The xor-longest Path

    题解: 在树上i到j的异或和可以直接转化为i到根的异或和^j到根的异或和. 所以我们把每个点到根的异或和处理出来放到trie里面,再把每个点放进去跑一遍即可. 代码: #include<cstd ...

  9. 为自己打造Linux小系统

     一.前言 Linux操作系统至1991.10.5号诞生以来,就源其开源性和自由性得到了很多技术大牛的青睐,每个Linux爱好者都为其贡献了自己的一份力,不管是在Linux内核还是开源软件等方面,都为 ...

  10. PopupWindow-弹窗的界面

      1 效果图 2 知识点 PopupWindow(View contentView, int width, int height) //创建一个没有获取焦点.长为width.宽为height,内容为 ...