The difference between HTML \ XHTML \xml

Although it is very simple knowledge, but if always in need of time to find, do not need to lose, it is always felt in the heart is not practical. Because you are like a garbage buy-out station, there is rubbish (knowledge) on the inside drag, drag not to lose some (forget). Not to tidy up, and therefore do not know what is lost is not important. For a while, you are still a garbage collector, hard to come by!

Classify the rubbish, summarize and comb, discard the minor part, make room to place the relative important thing, one day you will find that you have the precious wealth!

(1) XML
XML is shorthand for the extensible Markup Language (extensible Identity language). The current recommendation is to follow the XML1.0, published on October 6, 2000, for Reference (www.w3.org/TR/2000/REC-XML-20001006). Like HTML, XML is also derived from SGML, but XML is a language that can define other languages. XML was originally designed to compensate for the lack of HTML, with strong extensibility to meet the needs of network information dissemination, and then gradually used to transform and describe the network data. About the benefits of XML and technical specifications details here is not much to say, there is a lot of information on the Internet, there are many books can be consulted.  

(2) XHTML 
XHTML is an abbreviation for the extensible Hypertext Markup Language Extensible Identity language. It is recommended to follow the XML1.0 recommended on January 26, 2000 (refer to HTTP://WWW.W3.ORG/TR/XHTML1). XML is a powerful alternative to HTML, but it is premature to use XML directly in the face of thousands of existing sites. Therefore, based on HTML4.0, we extend it with XML rules and get XHTML. Simply put, the goal of XHTML is to make HTML transition to XML.  

(3) HTML
HTML is the universal language of the network, a simple, universal, all-in-one markup language. It allows web-makers to create complex pages of text and images that can be browsed by anyone else on the web, regardless of the type of computer or browser used. Is it magical? It's not magical at all, because now what you see is the page written in this language. haha. 

  HTML and XML: both of them are markup languages (ML), one is the hypertext labeling language, and the other is the extensible banner. 
the difference between them: 
1 Extensibility: HTML is not extensible, and XML is the original markup language that can be used to define new markup languages. 
2 Focus: HTML focuses on how to represent information, while XML is focused on how structured the descriptive information is. 
3 Syntax Requirements: HTML does not require tags of nesting, pairing, etc., do not require a certain order between tags, and XML is strict requirements of nesting, pairing, following the DTD tree structure. 
4 readability and maintainability: HTML is difficult to read and maintain, while XML structure is clear and easy to read and maintain
5 data and display relationships: HTML content description and display integration is unique, while XML is phase-separated
The last point is their editing tools, HTML has a bunch of editing tools, and XML is not yet mature. 

As for XHTML, it is a standard between HTML and XML, which is a requirement for HTML to conform to the XML syntax specification. However, the current browser support for XHTML is not very good.

Reference website: http://zhidao.baidu.com/question/24024660.html?qbl=relate_question_0&word=xhtml%D3%EBxml%B5%C4%C7%F8% B1%f0

http://zhidao.baidu.com/question/408219669.html?qbl=relate_question_1&word=xhtml%D3%EBxml%B5%C4%C7%F8%B1% F0&optimi=4

The difference between HTML \ XHTML \xml