About Html,xhtml,xml The difference between the three and my understanding

HTML and XML: both of them are markup languages (ML), one is the hypertext labeling language, and the other is the extensible banner.  Their differences: 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 difficult to read maintenance, and XML structure is clear, easy to read and maintain 5 of data and display relationships: HTML content description and display integration is unique, while XML is the last point of separation is their editor browsing tool, HTML has a bunch of editing browsing 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. 

(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) htmlhtml 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. You may have heard of a lot of software that can edit Web pages, in fact, you don't need any special software to create HTML pages; All you need is a word processor (such as Mcrosoftword\ Notepad, WordPad, and so on) and working knowledge of HTML. In fact, you will soon find that the underlying HTML language is simply dead. HTML is simply a series of labels that combine into a single text file. They are the conductor of the orchestra, telling musicians where to pause and where to be passionate. HTML tags are usually full names of English words (such as block references: BLOCKQUOTE) or abbreviations (such as "P" for Paragragh), but they differ from the general text because they are placed in a single title number. So the Paragragh tag is <p> The block reference tag is <blockquote>. Some labels explain how the page is formatted (for example,,<p> starts a new paragraph), and others show how the words are displayed (<b> make text thicker) there are other tags that provide information that is not displayed on the page-for example, the title. What you need to remember about labels is that they appear in pairs. Whenever a label is used-such as &LT;BLOCKQUOTE&GT, it must be closed with another label </blockquote>. Note the slash before "blockquote", which is the difference between closing the label and opening it. The basic HTML page starts with the 
About Html,xhtml,xml The difference between the three and my understanding