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XML Configuration File

2022-07-02 15:14:00 【Xiao afai_】

Believe in XML No stranger to developers , that , What is? XML Well ？XML What's the use ？ How to use XML Well ？ I believe you will have the answer after reading this article

This issue is wonderful

XML Attribute definitions

grammar

Attribute types

Property description

XML Example of attribute definition

XML The element definition of

1、DTD Definition

DTD brief introduction

DTD Specification example of

2、 Element definition

The classification of elements

The limit of the number of elements

Example of element definition

XML Introduce

XML What is it?

Extensible Markup Language（ Extensible markup language ）, abbreviation XML

Extensible markup language ：
1、 Mark , It refers to the information symbols that the computer can understand
2、 By such a mark , Computers can deal with articles containing all kinds of information

XML yes A format , It's a kind of Simple data storage language , It is also a commonly used configuration file

Use a series of simple tags to describe the data , And these tags can be created in a convenient way , The syntax format is strict , Although extensible markup language takes up more space than binary data , But extensible markup language is extremely simple and easy to master and use

XML The role of

Configuration file as a project or template
As the format of network transmission data ( Now JSON Mainly ).
To hold data , And the data are self descriptive

Why study XML

Extensible markup language is extremely simple and easy to master and use
The syntax format is strict , Is a common configuration file
XML Inside DTD( Now let's talk about ) Specifications can be defined , The function is equivalent to interface , That is, only by using this specification can we realize XML The function of

XML Attribute definitions

grammar

< !ATTLIST element-name att_name type desc >

Attribute types

ID： If it is written in an element, the element must have ID This attribute
( male | Woman )： Attributes can only be male or female , Write other errors
CDATA： Text attribute
IDREF： Quote someone else ID Value of label
reference( To use less )

Property description

#REQUIRED： It means required
#IMPLIED： Means not required
' The default value is '： Only type When it is male or female ,desc Can use the default value

XML Example of attribute definition

Make a statement person Property specification of object

XML The element definition of

1、DTD Definition

DTD brief introduction

DTD（ Document type definition ） The function of is to define XML The legal building blocks of documents

DTD It can be expressed in lines XML In the document , It can also be used as an external reference

DTD The label of ：< !DOCTYPE root[ ] >

DTD Specification example of

<!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>

]>

2、 Element definition

The classification of elements

< !DOCTYPE element-name EMPTY>// Empty elements 
< !DOCTYPE element-name (#PCDATA)>// Text elements 
< !DOCTYPE element-name (e1,e2)>// Mixed elements

notes ： An empty element refers to an element without a label body ( Photo label ), Such as </a>; Mixed elements refer to multiple different elements in an element , Such as <head> <h1> <sex> </sex> </h1></head>; Text elements are tags that can be passed in text types , Such as Chinese 、 Letter 、 Numbers etc.