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Detailed explanation of DTD

黄舟
黄舟Original
2017-02-20 15:06:112062browse

DTDDetailed explanation

##Basic overview


Document Type Definition

(Document Type Definition) is a set of grammatical rules about tags established for data exchange between programs. It is part of the Standard Generalized Markup Language (SGML) and Extensible Markup Language (XML) version 1.0, and is documented under Some DTD syntax rule verifies that the format conforms to this rule. Document type definitions can also be used to ensure the legality of standard universal markup language and extensible markup language document formats. You can compare documents with document type definition files to check whether the document conforms to the specification and whether the elements and tags are used correctly. File instances provide applications with a format for exchanging data.

PS: In short, DTD is used to constrain XML document, so that it can be used under certain specifications. In addition to DTD technology, there is also Schema technology, which is also used For constrained XML documents.

Reference document:

DTD http://www.php.cn/

Reference document:

Schema http://www.php.cn/

DTD

Schematic

PS: Constrained by DTD, XML can be customized under the constraints of DTD, but DTD has A disadvantage is that it cannot impose range constraints such as numerical constraints on the data.

DTD

Declaration and reference of document

Internal

DTDDocumentation

##d5896d8fab48258bc5208998b65f8a25External

DTD

Document

c9fe9a999289c144839afaf84993cb83Internal and external

DTD

Document combination

c49cc1bbed7f32fc382766a582d38140Note:

1

, definition keywords must be capitalized, for example:

DOCTYPE, ELEMENT, ATTLIST. 2

,

When the referenced file is local, the following method is used:

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For example: 96e41340e472072b366436fa660bd81f

When the referenced file is a public file, the following method is used:

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##For example: f6b23a4dcfcf2a7ce51a065861e67dc3

DTD

Element

Basic Grammar

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Explanation:

ELEMENT: Keyword

(must be capitalized).

NAME

: Element name.

CONTENT

: There are four element types, all of which must be capitalized.

1EMPTY-This element cannot contain sub-elements and text, but it can have attributes (empty elements)

## 2

ANY-This element can contain anything in DTD## Element content defined in # 3

#PCDATA-can contain any character data, but cannot It contains any sub-elements## 4, other types

(combination), can be a sub-element, a combination of sub-element and modifier, a combination of basic element, sub-element and modifier. Case:

3ceb8b302a752410845e00ddf5488f8126ed0e6047a1db75d76d12a6f7876de0< ;!ELEMENT Author

(#PCDATA)>

ded3ccbb88539977f7ea6146fb2375b4

772d6896d7a6727c85d7ccfd9db439a3

8847d77a032f4f9263c9eeda19e6e8c1

Modifier

Symbol##This object is allowed to appear zero to any number of times ( (HobbyHobby can appear zero to multiple times?This object can appear, But it can only appear once (Rookie,,

Use

Example

Example description

( )

Used to group elements

(古龙|Jin Yong|Liang Yusheng),(Wang Shuo|Yu Jie)

Divided into two groups

|

Select one of the listed objects

(Men|Women)

means that a man or a woman must appear, and you can only choose one

##+

The object appears at least once and can appear multiple times

(1 or multiple times)

(Member

+

indicates that the member must appear, and multiple members can appear Member

*

0

to many times)

*

)

(0

to 1 times)

?

##The rookie can appear or not. If it appears, Can only appear once at most

Objects must appear in the specified order

(Watermelon

Apple,banana) ## means watermelon, apple, banana must appear, and appear in this order

# #


##DTD

Attributes

Basic Syntax


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Explanation:

ATTLIST

: attribute list, (must be capitalized ).

Element name: The name of the corresponding element.

Attribute: There can be multiple attributes, and the format is name type attribute property

Type:


##PS

: Commonly used ones are

CDATA(Character type), enumeration (The enumeration format is (value1| Value2|Value3...)),ID(ID cannot be repeated and cannot start with a number ), IDREF( refers to another IDValue),IDREFS(can reference multiple ID Values, separated by spaces )

Attribute characteristics are:


Case:

<!ELEMENT 班级 (学生+,作者)>
<!ATTLIST 班级
	班次 CDATA "1班"
	编号 ID #REQUIRED
>
<!ELEMENT 学生 (名字,年龄,介绍)>
<!ELEMENT 作者 (#PCDATA)>
<!ATTLIST 学生
	地址 CDATA #IMPLIED
	授课方式 CDATA #FIXED "面授"
	学号 ID #REQUIRED
	班级编号 IDREF #REQUIRED
	朋友 IDREFS #IMPLIED
>
<!ELEMENT 名字 (#PCDATA)>
<!ELEMENT 年龄 (#PCDATA)>
<!ELEMENT 介绍 (#PCDATA)>

Entity

There are two types of entities: reference entities and parameter entities. Reference entities are generally used in

XML

, and parameter entities are generally used in DTD. Basic syntax

##30c188cd2a4b3e112bcbcf3f63ba1049 // Reference entity##dcb0500563c952f8097a4d6ee0799e77 // Parameter entityExplanation: 1, the reference entity can be referenced

DTD

XML file, use &entity name; to use entity content. 2. I don’t know if it’s because of my computer. You can’t use reference entities in external DTD

. If you use it, put the reference entity definition in In the internal DTD, it can be used. 3, parameter entity is used in DTD

, use %entity name;use

4、可以将那些重复使用的值定义成实体,这样能减少代码的冗余度。

5、在外部DTD中,引用实体最好放在DTD底部,参数实体最好放在DTD顶部。

 

案例:

<!ENTITY % sex "男|女">
<!ELEMENT 班级 (学生+,作者)>
<!ELEMENT 学生 (名字,年龄,介绍)>
<!ELEMENT 作者 (#PCDATA)>
<!ATTLIST 学生
	性别 (%sex;) #REQUIRED
>
<!ELEMENT 名字 (#PCDATA)>
<!ELEMENT 年龄 (#PCDATA)>
<!ELEMENT 介绍 (#PCDATA)>
<!ENTITY writer "Switch">


综合案例1

XML3.dtd

<!ENTITY % sex "男|女">
<!ELEMENT 班级 (学生+,作者)>
<!ATTLIST 班级
	班次 CDATA "1班"
	编号 ID #REQUIRED
>
<!ELEMENT 学生 (名字,年龄,介绍)>
<!ELEMENT 作者 (#PCDATA)>
<!ATTLIST 学生
	地址 CDATA #IMPLIED
	授课方式 CDATA #FIXED "面授"
	学号 ID #REQUIRED
	班级编号 IDREF #REQUIRED
	朋友 IDREFS #IMPLIED
	性别 (%sex;) #REQUIRED
>
<!ELEMENT 名字 (#PCDATA)>
<!ELEMENT 年龄 (#PCDATA)>
<!ELEMENT 介绍 (#PCDATA)>


XML3.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- 引入DTD -->
<!DOCTYPE 班级 SYSTEM "XML3.dtd"
[<!ENTITY writer "Switch">]>
<班级 编号="C1" 班次="1班">
	<学生  地址="湖南" 授课方式="面授" 学号="n1" 班级编号="C1" 朋友="n2" 性别="男">
		<名字>张三</名字>
		<年龄>20</年龄>
		<介绍>不错</介绍>
	</学生>
	<学生 授课方式="面授" 学号="n2" 班级编号="C1" 朋友="n1 n3" 性别="女">
		<名字>李四</名字>
		<年龄>18</年龄>
		<介绍>很好</介绍>
	</学生>
	<学生 授课方式="面授" 学号="n3" 班级编号="C1" 朋友="n2" 性别="男">
		<名字>王五</名字>
		<年龄>22</年龄>
		<介绍>非常好</介绍>
	</学生>
	<作者>&writer;</作者>
</班级>


综合案例2

XML4.dtd

<!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)>


XML4.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE CATALOG SYSTEM "XML4.dtd">
<CATALOG>
	<PRODUCT NAME="C&#39;estbon" CATEGORY="Shop-Professional" INVENTORY="Backordered" PARTNUM="10" PLANT="Chicago">
		<SPECIFICATIONS POWER="0" WEIGHT="555ml">SPECIFICATIONS</SPECIFICATIONS>
		<OPTIONS>OPTIONS</OPTIONS>
		<PRICE>2</PRICE>
		<NOTES>NOTES</NOTES>
	</PRODUCT>
</CATALOG>

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