xml文件中的DOCTYPE的含义是什么？ [英] What is the meaning of DOCTYPE in xml file?

问题描述

在hibernate中，我们使用配置和映射xml文件。
在xml中，第一行是版本，然后我们指定DOCTYPE DTD行。
示例：

 <！DOCTYPE hibernate-mapping PUBLIC -  // Hibernate / Hibernate Mapping DTD 3.0 // ENhttp://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd\"> 
  

任何人都可以解释一下这是什么意思吗？
我知道DTD是文档类型定义，就像为XML定义语法一样。

我想知道这个声明中的属性。 您引用的行是文档类型声明。

W3C的XML推荐文档中记载了 http://www.w3.org/TR/xml/#dt-doctype

它指定处理文档时要使用的DTD。有两种机制可用于指定这个

1. 一个可选的PUBLIC标识符（很少这些
   天）例如，
   - // Hibernate / Hibernate Mapping DTD 3.0 // EN。解析为DTD资源
   的机制是特定于应用程序的。
   

2. SYSTEM
   标识符，在您的示例中是
   http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd。
   这通常被解释为一个
   的URL，其中DTD可以是
   检索的位置。
   

In hibernate we use configuration and mapping xml files. In xml the first line will be version and then we specify DOCTYPE DTD line. Example:

<!DOCTYPE hibernate-mapping PUBLIC  "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

Can anybody please explain what is the meaning of this? I know that DTD is document type definition which is like defining grammar for the xml.

I want to know the attributes in this statement.

解决方案

The line you refer to is the document type declaration.

It is documented in the W3C's XML Recommendation here: http://www.w3.org/TR/xml/#dt-doctype

It specifies a DTD that is to be used when processing the document. Two mechanisms are available for specifying this

1. an optional PUBLIC identifier (rare these days) which is, in your example, " -//Hibernate/Hibernate Mapping DTD 3.0//EN". The mechanism by which this is resolved to a DTD resource is application-specific.

2. A SYSTEM identifier, which in your example is "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd". This is typically interpreted as a URL from where the DTD can be retrieved.

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