WebService (2)-DTD of the XML series, webservice-xml

WebService (2)-DTD of the XML series, webservice-xml
Source code download: Link: http://pan.baidu.com/s/1jGzSw5o password: ftgw A. Definition

Document Type Definition DTD (Document Type Definition) is used to detect whether XML complies with syntax rules.

Ii. Instance

Two Methods of document type declaration:

1. Internal Definition

Persons. xml file

<? Xml version = "1.0" encoding = "UTF-8"?> <! -- <! DOCTYPE root element [element Declaration]> --> <! DOCTYPE persons [<! -- Common control operator :?: 0-1; *: 0-N; +: 1-N; default: 1 --> <! ELEMENT persons (person +)> <! ELEMENT person (name, password, age)> <! -- # PCDATA is a term used by the XML parser to parse text data --> <! -- CDATA appears in the attribute declaration --> <! ELEMENT name (# PCDATA)> <! ELEMENT password (# PCDATA)> <! ELEMENT age (# PCDATA)> <! -- # The REQUIRED attribute value is REQUIRED --> <! -- # The IMPLIED attribute is not required --> <! -- # The FIXED value attribute value is FIXED --> <! -- The ID value is a unique id --> <! ATTLIST person id # REQUIRED> <! -- The CDATA value is character data --> <! ATTLIST person email CDATA # REQUIRED>]> <persons> <person id = "p1070541038" email = "452274335@qq.com"> <name> Zhao Li Jing </name> <password> 000000 </password> <age> 26 </age> <! -- <Id> p1070541038 </id> --> <! -- Incorrect syntax --> <! -- <Email> 452274335@qq.com </email> --> </person> <person id = "p2070541038" email = "552274335@qq.com"> <name> Zhao Li Kai </name> <password> 000000 </password> <age> 26 </age> </person> </persons>

2. External Definition

Classroom. dtd file

<?xml version="1.0" encoding="UTF-8"?><!ELEMENT classroom (name,grade,students)><!ATTLIST classroom id ID #REQUIRED><!ELEMENT name (#PCDATA)><!ELEMENT grade (#PCDATA)><!ELEMENT students (student+)><!ELEMENT student (id,name,age)><!ELEMENT id (#PCDATA)><!ELEMENT name (#PCDATA)><!ELEMENT age (#PCDATA)>

Classroom. xml file

<? Xml version = "1.0" encoding = "UTF-8"?> <! -- 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 classroom SYSTEM "classroom. dtd "> <classroom id =" classroomid1 "> <name> classname1 </name> <grade> grade1 </grade> <students> <student> <id> studentid1 </id> <name> studentname1 </name> <age> studentage1 </age> </student> <id> studentid2 </id> <name> studentname2 </name> <age> studentage2 </age> </student> </students> </classroom>

Iii. Comments 1. Advantages:

Simple and Easy to write.

Check whether XML is valid

2. Disadvantages:

1) different from XML syntax
2) provides a limited number of data types, and users cannot customize the data types.

3) The domain name mechanism is not supported

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