How do you refer a book to your friend? Take for example, you want to refer the book “Introduction to algorithms by Cormen”, you would say in the following manner
Book: Introduction to Algorithms
Authors: Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, Clifford Stein
This is clearly understood by anybody. But as far as search engines are concerned, this is some raw information. They cannot make any meaning out of it. Similar is the case with softwares, because different people will write the information in different manners. Some will write the book title after the authors’ names. Others will prefer not to specify the edition.
So there must be a way by which data can be transferred in a manner which is receptive both at the receiving end and the sender.
XML is a markup language to represent the data. Unlike HTML, which has a fixed number of tafs like head, title, body, h1, h2, p, XML allows any user generated tags. The user generated tags must be known at both the ends. Even if it is not known, various information can be pulled out.
This use of user generated tags has resulted in the development of XHTML, RSS and Atom from XML. In fact many other standards make use of XML to represent various information.
To make the above things clear, I will write the above information in XML format
<?xml version="1.0" encoding=’UTF-8′?>
<title>Introduction to Algorithms</title>
<author>Thomas H. Cormen</author>
<author>Charles E. Leiserson</author>
<author>Ronald L. Rivest</author>
As you can see, the above format is more clear and can be used to extract information. Therefore if the template is known, a lot of things can be inferred. In fact, a lot of standards gradually develop by using information in such structured format.