Html, Xml, and Xhtml
Html stands for Hyper Text Markup Language. It is a markup set that has been used widely for transferring information over the web, since it is first used in 1990.
The problem of Html is the markup set is fixed, and Html tags are expressionless. Xml, stand for extensible markup language is totally different. You can define and create expressive tags that would make the transferred information becomes more meaningful. Also, Xml has strictly syntax and structure, forcing the document to be well formed. Xml certainly have advantages over html. How ever, Html has existed for years, and being adopted widely in web pages and web browsers, which could make it hardly to be changed.
Xhtml, stand for extensible hypertext markup language, addresses the requirement of both Xml and Html. To be able to do so, Xhtml has to overcome the syntax difference. Some tags of html don’t require to be closed, for example image tag can be written as <img src=”imagesource.jpg”>. Xml is different, it requires every tag to be closed or there will be an error when processing the document. Xml tags can be self closed, and the above example can be rewrite as <img src=”imagesource.jpg” />. Xhmlcan use the same closing tag. When being read as Html, the slash will be treated as an attribute, and because the attribute is invalid then it will be omitted. So <img src=”imagesource.jpg” /> will be the same as “<img src=”imagesource.jpg”>.
By using Xhtml, web applications can display information by using classic html tags, while having the extensible capability of Xml to define new tags when necessary.
