Crazy XML study notes (3) -----------XML and DTD
Document type definition (DTD) can define legal XML document building blocks. It uses a series of legal elements to define the structure of the document.
DTD can be declared in an XML document as a line or as an external reference.
##Internal DOCTYPE declaration
If the DTD is included in your XML source file, it should pass the following syntax Wrapped in a DOCTYPE declaration:
<!DOCTYPE 根元素 [元素声明]>
XML document instance with DTD
<?xml version="1.0"?> <!DOCTYPE note [ <!ELEMENT note (to,from,heading,body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)> ]> <note> <to>George</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget the meeting!</body> </note>
The above DTD is explained as follows:
!DOCTYPE note (second line) defines this document as a note type document.
!ELEMENT note (Third line) Definition note The element has four elements: "to, from, heading,, body"
!ELEMENT to (Fourth line) defines the to element as "#PCDATA" type
!ELEMENT from (fifth line) defines the frome element as "#PCDATA" type
!ELEMENT heading (Sixth line) Definition heading The element is "#PCDATA" type
!ELEMENT body (Seventh line) Definitionbody The element is "#PCDATA" type
External document declaration
If the DTD is located outside the XML source file, it should be encapsulated in a DOCTYPE definition using the following syntax:
<!DOCTYPE 根元素 SYSTEM "文件名">
This XML document is the same as the XML document above, but Have an external DTD: (And select the "View Source" command.)
<?xml version="1.0"?> <!DOCTYPE note SYSTEM "note.dtd"> <note> <to>George</to> <from>John</from> <heading>Reminder</heading> <body>Don't forget the meeting!</body> </note>
This is the "note.dtd" file containing the DTD:
<!ELEMENT note (to,from,heading,body)> <!ELEMENT to (#PCDATA)> <!ELEMENT from (#PCDATA)> <!ELEMENT heading (#PCDATA)> <!ELEMENT body (#PCDATA)>
Why use DTD?
#With a DTD, each of your XML files can carry a description of its own format.
With DTD, independent groups can consistently use a standard DTD to exchange data.
Your application can also use a standard DTD to verify data received from the outside.
You can also use DTDs to validate your own data.
XML document building module
All XML documents (as well as HTML documents) are composed of the following simple building blocks:
Elements
Attributes
Entity
PCDATA
CDATA
The following is a brief description of each building block.
Elements
Elements are the main building blocks of XML and HTML documents .
Examples of HTML elements are "body" and "table". Examples of XML elements are "note" and "message" . Elements can contain text, other elements, or be empty. Examples of empty HTML elements are "hr", "br", and "img".
Instance: <body>body text in between</body>
<message>some message in between</message>
Copy after login
<body>body text in between</body> <message>some message in between</message>
Attributes
Attributes provide additional information about the element.
Attributes are always placed in the opening tag of an element. Properties always appear in name/value pairs. The following "img" element holds additional information about the source file:
<img src="computer.gif" />
The name of the element is "img". The name of the attribute is "src". The value of the property is "computer.gif". Since the element itself is empty, it is closed with a " /".
entity
实体是用来定义普通文本的变量。实体引用是对实体的引用。
大多数同学都了解这个 HTML 实体引用：" "。这个“无折行空格”实体在 HTML 中被用于在某个文档中插入一个额外的空格。
当文档被 XML 解析器解析时，实体就会被展开。
下面的实体在 XML 中被预定义：
| 实体引用 | 字符 |
|---|---|
| < | < |
| > | > |
| & | & |
| " | " |
| ' | ' |
PCDATA
PCDATA 的意思是被解析的字符数据（parsed character data）。
可把字符数据想象为 XML 元素的开始标签与结束标签之间的文本。
PCDATA 是会被解析器解析的文本。这些文本将被解析器检查实体以及标记。
文本中的标签会被当作标记来处理，而实体会被展开。
不过，被解析的字符数据不应当包含任何 &、< 或者 > 字符；需要使用 &、< 以及 > 实体来分别替换它们。
在一个 DTD 中，元素通过元素声明来进行声明。
声明一个元素
在 DTD 中，XML 元素通过元素声明来进行声明。元素声明使用下面的语法：
<!ELEMENT 元素名称 类别>
或者
<!ELEMENT 元素名称 (元素内容)>
空元素
空元素通过类别关键词EMPTY进行声明：
<!ELEMENT 元素名称 EMPTY>
例子：
<!ELEMENT br EMPTY>
XML例子：
<br />
只有 PCDATA 的元素
只有 PCDATA 的元素通过圆括号中的 #PCDATA 进行声明：
<!ELEMENT 元素名称 (#PCDATA)>
例子：
<!ELEMENT from (#PCDATA)>
带有任何内容的元素
通过类别关键词 ANY 声明的元素，可包含任何可解析数据的组合：
<!ELEMENT 元素名称 ANY>
例子：
<!ELEMENT note ANY>
带有子元素（序列）的元素
带有一个或多个子元素的元素通过圆括号中的子元素名进行声明：
<!ELEMENT 元素名称 (子元素名称 1)>
或者
<!ELEMENT 元素名称 (子元素名称 1,子元素名称 2,.....)>
例子：
<!ELEMENT note (to,from,heading,body)>
当子元素按照由逗号分隔开的序列进行声明时，这些子元素必须按照相同的顺序出现在文档中。在一个完整的声明中，子元素也必须被声明，同时子元素也可拥有子元素。"note" 元素的完整声明是：
<!ELEMENT note (to,from,heading,body)>
声明只出现一次的元素
<!ELEMENT 元素名称 (子元素名称)>
例子：
<!ELEMENT note (message)>
上面的例子声明了：message 子元素必须出现一次，并且必须只在 "note" 元素中出现一次。
声明最少出现一次的元素
<!ELEMENT 元素名称 (子元素名称+)>
例子：
<!ELEMENT note (message+)>
上面的例子中的加号声明了：message 子元素必须在 "note" 元素内出现至少一次。
声明出现零次或多次的元素
<!ELEMENT 元素名称 (子元素名称*)>
例子：
<!ELEMENT note (message*)>
上面的例子中的星号声明了：子元素 message 可在 "note" 元素内出现零次或多次。
声明出现零次或一次的元素
<!ELEMENT 元素名称 (子元素名称?)>
例子：
<!ELEMENT note (message?)>
上面的例子中的问号声明了：子元素 message 可在 "note" 元素内出现零次或一次。
声明“非.../既...”类型的内容
例子：
<!ELEMENT note (to,from,header,(message|body))>
上面的例子声明了："note" 元素必须包含 "to" 元素、"from" 元素、"header" 元素，以及非 "message" 元素既 "body" 元素。
声明混合型的内容
例子：
<!ELEMENT note (#PCDATA|to|from|header|message)*>
上面的例子声明了："note" 元素可包含出现零次或多次的 PCDATA、"to"、"from"、"header" 或者 "message"。
声明属性
属性声明拥使用下列语法：
<!ATTLIST 元素名称 属性名称 属性类型 默认值>
DTD 实例:
<!ATTLIST payment type CDATA "check">
XML 实例:
<payment type="check" />
以下是属性类型的选项：
| 类型 | 描述 |
|---|---|
| CDATA | 值为字符数据 (character data) |
| (en1|en2|..) | 此值是枚举列表中的一个值 |
| ID | 值为唯一的 id |
| IDREF | 值为另外一个元素的 id |
| IDREFS | 值为其他 id 的列表 |
| NMTOKEN | 值为合法的 XML 名称 |
| NMTOKENS | 值为合法的 XML 名称的列表 |
| ENTITY | 值是一个实体 |
| ENTITIES | 值是一个实体列表 |
| NOTATION | 此值是符号的名称 |
| xml: | 值是一个预定义的 XML 值 |
默认值参数可使用下列值：
| 值 | 解释 |
|---|---|
| 值 | 属性的默认值 |
| #REQUIRED | 属性值是必需的 |
| #IMPLIED | 属性不是必需的 |
| #FIXED value | 属性值是固定的 |
规定一个默认的属性值
DTD:
<!ELEMENT square EMPTY> <!ATTLIST square width CDATA "0">
合法的 XML:
<square width="100" />
在上面的例子中，"square" 被定义为带有 CDATA 类型的 "width" 属性的空元素。如果宽度没有被设定，其默认值为0 。
#IMPLIED
语法
<!ATTLIST 元素名称 属性名称 属性类型 #IMPLIED>
例子
DTD:
<!ATTLIST contact fax CDATA #IMPLIED>
合法的 XML:
<contact fax="555-667788" />
合法的 XML:
<contact />
假如您不希望强制作者包含属性，并且您没有默认值选项的话，请使用关键词 #IMPLIED。
#REQUIRED
语法
<!ATTLIST 元素名称 属性名称 属性类型 #REQUIRED>
例子
DTD:
<!ATTLIST person number CDATA #REQUIRED>
合法的 XML:
<person number="5677" />
非法的 XML:
<person />
假如您没有默认值选项，但是仍然希望强制作者提交属性的话，请使用关键词 #REQUIRED。
#FIXED
语法
<!ATTLIST 元素名称 属性名称 属性类型 #FIXED "value">
例子
DTD:
<!ATTLIST sender company CDATA #FIXED "Microsoft">
合法的 XML:
<sender company="Microsoft" />
非法的 XML:
<sender company="W3School" />
如果您希望属性拥有固定的值，并不允许作者改变这个值，请使用 #FIXED 关键词。如果作者使用了不同的值，XML 解析器会返回错误。
列举属性值
语法：
<!ATTLIST 元素名称 属性名称 (en1|en2|..) 默认值>
DTD 例子:
<!ATTLIST payment type (check|cash) "cash">
XML 例子:
<payment type="check" />
或者
<payment type="cash" />
如果您希望属性值为一系列固定的合法值之一，请使用列举属性值。
实体是用于定义用于定义引用普通文本或特殊字符的快捷方式的变量。
实体引用是对实体的引用。
实体可在内部或外部进行声明。
一个内部实体声明
语法：
<!ENTITY 实体名称 "实体的值">
例子：
DTD 例子:
<!ENTITY writer "Bill Gates"> <!ENTITY copyright "Copyright W3School.com.cn">
XML 例子:
<author>&writer;©right;</author>
注释: 一个实体由三部分构成: 一个和号 (&), 一个实体名称, 以及一个分号 (;)。
一个外部实体声明
语法：
<!ENTITY 实体名称 SYSTEM "URI/URL">
例子：
DTD 例子:
<!ENTITY writer SYSTEM "http://www.w3school.com.cn/dtd/entities.dtd"> <!ENTITY copyright SYSTEM "http://www.w3school.com.cn/dtd/entities.dtd">
XML 例子:
<author>&writer;©right;</author>
通过 XML 解析器进行验证
当您试图打开某个 XML 文档时，XML 解析器有可能会产生错误。通过访问 parseError 对象，就可以取回引起错误的确切代码、文本甚至所在的行。
注释：load( ) 方法用于文件，而 loadXML( ) 方法用于字符串。
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.validateOnParse="true"
xmlDoc.load("note_dtd_error.xml")
document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)
关闭验证
通过把 XML 解析器的 validateOnParse 设置为 "false"，就可以关闭验证。
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.validateOnParse="false"
xmlDoc.load("note_dtd_error.xml")
document.write("<br>Error Code: ")
document.write(xmlDoc.parseError.errorCode)
document.write("<br>Error Reason: ")
document.write(xmlDoc.parseError.reason)
document.write("<br>Error Line: ")
document.write(xmlDoc.parseError.line)Try it Yourself
通用的 XML 验证器
为了帮助您验证 XML 文件，我们创建了此链接，这样你就可以验证任何 XML 文件了。
parseError 对象
电视节目表 DTD
<!DOCTYPE TVSCHEDULE [ <!ELEMENT TVSCHEDULE (CHANNEL+)> <!ELEMENT CHANNEL (BANNER,DAY+)> <!ELEMENT BANNER (#PCDATA)> <!ELEMENT DAY (DATE,(HOLIDAY|PROGRAMSLOT+)+)> <!ELEMENT HOLIDAY (#PCDATA)> <!ELEMENT DATE (#PCDATA)> <!ELEMENT PROGRAMSLOT (TIME,TITLE,DESCRIPTION?)> <!ELEMENT TIME (#PCDATA)> <!ELEMENT TITLE (#PCDATA)> <!ELEMENT DESCRIPTION (#PCDATA)> <!ATTLIST TVSCHEDULE NAME CDATA #REQUIRED> <!ATTLIST CHANNEL CHAN CDATA #REQUIRED> <!ATTLIST PROGRAMSLOT VTR CDATA #IMPLIED> <!ATTLIST TITLE RATING CDATA #IMPLIED> <!ATTLIST TITLE LANGUAGE CDATA #IMPLIED> ]>
报纸文章 DTD
<!DOCTYPE NEWSPAPER [ <!ELEMENT NEWSPAPER (ARTICLE+)> <!ELEMENT ARTICLE (HEADLINE,BYLINE,LEAD,BODY,NOTES)> <!ELEMENT HEADLINE (#PCDATA)> <!ELEMENT BYLINE (#PCDATA)> <!ELEMENT LEAD (#PCDATA)> <!ELEMENT BODY (#PCDATA)> <!ELEMENT NOTES (#PCDATA)> <!ATTLIST ARTICLE AUTHOR CDATA #REQUIRED> <!ATTLIST ARTICLE EDITOR CDATA #IMPLIED> <!ATTLIST ARTICLE DATE CDATA #IMPLIED> <!ATTLIST ARTICLE EDITION CDATA #IMPLIED> <!ENTITY NEWSPAPER "Vervet Logic Times"> <!ENTITY PUBLISHER "Vervet Logic Press"> <!ENTITY COPYRIGHT "Copyright 1998 Vervet Logic Press"> ]>
产品目录 DTD
拷贝自：http://www.php.cn/
<!DOCTYPE CATALOG [ <!ENTITY AUTHOR "John Doe"> <!ENTITY COMPANY "JD Power Tools, Inc."> <!ENTITY EMAIL "jd@jd-tools.com"> <!ELEMENT CATALOG (PRODUCT+)> <!ELEMENT PRODUCT (SPECIFICATIONS+,OPTIONS?,PRICE+,NOTES?)> <!ATTLIST PRODUCT NAME CDATA #IMPLIED CATEGORY (HandTool|Table|Shop-Professional) "HandTool" PARTNUM CDATA #IMPLIED PLANT (Pittsburgh|Milwaukee|Chicago) "Chicago" INVENTORY (InStock|Backordered|Discontinued) "InStock"> <!ELEMENT SPECIFICATIONS (#PCDATA)> <!ATTLIST SPECIFICATIONS WEIGHT CDATA #IMPLIED POWER CDATA #IMPLIED> <!ELEMENT OPTIONS (#PCDATA)> <!ATTLIST OPTIONS FINISH (Metal|Polished|Matte) "Matte" ADAPTER (Included|Optional|NotApplicable) "Included" CASE (HardShell|Soft|NotApplicable) "HardShell"> <!ELEMENT PRICE (#PCDATA)> <!ATTLIST PRICE MSRP CDATA #IMPLIED WHOLESALE CDATA #IMPLIED STREET CDATA #IMPLIED SHIPPING CDATA #IMPLIED> <!ELEMENT NOTES (#PCDATA)> ]>
以上就是疯狂XML学习笔记（3）-----------XML与DTD 的内容，更多相关内容请关注PHP中文网（www.php.cn）！
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
1378
52
Can I open an XML file using PowerPoint?
Feb 19, 2024 pm 09:06 PM
Can XML files be opened with PPT? XML, Extensible Markup Language (Extensible Markup Language), is a universal markup language that is widely used in data exchange and data storage. Compared with HTML, XML is more flexible and can define its own tags and data structures, making the storage and exchange of data more convenient and unified. PPT, or PowerPoint, is a software developed by Microsoft for creating presentations. It provides a comprehensive way of
Using Python to merge and deduplicate XML data
Aug 07, 2023 am 11:33 AM
Using Python to merge and deduplicate XML data XML (eXtensibleMarkupLanguage) is a markup language used to store and transmit data. When processing XML data, sometimes we need to merge multiple XML files into one, or remove duplicate data. This article will introduce how to use Python to implement XML data merging and deduplication, and give corresponding code examples. 1. XML data merging When we have multiple XML files, we need to merge them
Filtering and sorting XML data using Python
Aug 07, 2023 pm 04:17 PM
Implementing filtering and sorting of XML data using Python Introduction: XML is a commonly used data exchange format that stores data in the form of tags and attributes. When processing XML data, we often need to filter and sort the data. Python provides many useful tools and libraries to process XML data. This article will introduce how to use Python to filter and sort XML data. Reading the XML file Before we begin, we need to read the XML file. Python has many XML processing libraries,
Convert XML data to CSV format in Python
Aug 11, 2023 pm 07:41 PM
Convert XML data in Python to CSV format XML (ExtensibleMarkupLanguage) is an extensible markup language commonly used for data storage and transmission. CSV (CommaSeparatedValues) is a comma-delimited text file format commonly used for data import and export. When processing data, sometimes it is necessary to convert XML data to CSV format for easy analysis and processing. Python is a powerful
Import XML data into database using PHP
Aug 07, 2023 am 09:58 AM
Importing XML data into the database using PHP Introduction: During development, we often need to import external data into the database for further processing and analysis. As a commonly used data exchange format, XML is often used to store and transmit structured data. This article will introduce how to use PHP to import XML data into a database. Step 1: Parse the XML file First, we need to parse the XML file and extract the required data. PHP provides several ways to parse XML, the most commonly used of which is using Simple
Python implements conversion between XML and JSON
Aug 07, 2023 pm 07:10 PM
Python implements conversion between XML and JSON Introduction: In the daily development process, we often need to convert data between different formats. XML and JSON are common data exchange formats. In Python, we can use various libraries to convert between XML and JSON. This article will introduce several commonly used methods, with code examples. 1. To convert XML to JSON in Python, we can use the xml.etree.ElementTree module
Handling errors and exceptions in XML using Python
Aug 08, 2023 pm 12:25 PM
Handling Errors and Exceptions in XML Using Python XML is a commonly used data format used to store and represent structured data. When we use Python to process XML, sometimes we may encounter some errors and exceptions. In this article, I will introduce how to use Python to handle errors and exceptions in XML, and provide some sample code for reference. Use try-except statement to catch XML parsing errors When we use Python to parse XML, sometimes we may encounter some
Python parsing special characters and escape sequences in XML
Aug 08, 2023 pm 12:46 PM
Python parses special characters and escape sequences in XML XML (eXtensibleMarkupLanguage) is a commonly used data exchange format used to transfer and store data between different systems. When processing XML files, you often encounter situations that contain special characters and escape sequences, which may cause parsing errors or misinterpretation of the data. Therefore, when parsing XML files using Python, we need to understand how to handle these special characters and escape sequences. 1. Special characters and
