XML介绍

XML Extensible Markup Language 扩展标记语言

xml spec 1.1
https://www.w3.org/TR/2006/REC-xml11-20060816/
中文版课程
http://www.w3school.com.cn/xml/index.asp
一种类似树结构的文档

由各级元素组成,元素分为根元素和子元素

元素有属性和值

元素有开始标签start-tag和结束标签end-tag

开始标签<TagName>

结束标签</TagName>

注释

<!-- This is a comment -->

XML 以 LF 作为换行符

XML 命名空间namespaces 用来避免元素命名冲突
https://www.w3.org/TR/2009/REC-xml-names-20091208/
The prefix xml is by definition bound to the namespace name http://www.w3.org/XML/1998/namespace. It MAY, but need not, be declared, and MUST NOT be bound to any other namespace name. Other prefixes MUST NOT be bound to this namespace name, and it MUST NOT
be declared as the default namespace.

The prefix xmlns is used only to declare namespace bindings and is by definition bound to the namespace name http://www.w3.org/2000/xmlns/. It MUST NOT be declared . Other prefixes MUST NOT be bound to this namespace name, and it MUST NOT be declared as the
default namespace. Element names MUST NOT have the prefix xmlns.

The namespace prefix, unless it is xml or xmlns, MUST have been declared in a namespace declaration attribute in either the start-tag of the element where the prefix is used or in an ancestor element (i.e., an element in whose content the prefixed markup occurs).