XML History & Information

The first question that anybody could ask is “What is XML? ” XML is an acronym for Extensible Markup Language. XML is a markup language derived from SGML. An XML document is written using the markup language to contain structured information. A mark up makes it easy to identify structures within a document.

In this content, we describe a document as a data file containing information and reference to data in various formats and purpose including but not limited to mathematical equations, vector graphics, e-commerce transaction details, , object meta-data, server APIs, and various other structured information.

Structured Content in an XML document may contain Words, pictures and a description of the relationship of the content within. XML is different from HTML. In HTML tag semantics and tag sets are fixed and rigidly defined. To make it simpler look at the example below:

Example of a raw data and information:
John Doe
Ace Corporation
Ace Building
1 Ace Drive Way
Sometown SomeState
USA 99999
213 244 56321

Basic HTML output:
John Doe
Ace Corporation
Ace Building
1 Ace Drive Way
Sometown SomeState
USA 99999
213 244 56321

The above HTML output can be derived from many of the different HTML tags available. We can use these HTML code below for the said output:

<strong>John Doe</strong><br />
<strong><em>Ace Corporation</em></strong><br />
<strong><em>Ace Building</em></strong><br />
<strong><em>1 Ace Drive Way</em></strong><br />
<strong>Sometown SomeState</strong><br />
<strong>USA 99999</strong><br />
<strong>213 244 56321</strong>

Or may be written as the later HTML tags which is:

<bold>John Doe</bold><br />
<bold><i>Ace Corporation</i></bold><br />
<bold><i>Ace Building</i></bold><br />
<bold><i>1 Ace Drive Way</i></bold><br />
<bold>Sometown SomeState</bold><br />
<bold>USA 99999</bold><br />
<bold>213 244 56321</bold>

A simple XML data record would be the following:

<Address Book>
    <Full name>John Doe </Full name>
    <Company Name>Ace Corporation</Company Name>
    <Address Line 1>Ace Building</Address Line 1>
    <Address Line 2>1 Ace Drive Way</Address Line 2>
    <City>Some Town</City> <State> Some State</State>
    <Country>USA</Country> <Postal Code>99999</Postal Code>
    <Phone Number>213 244 56321</Phone Number>
</Address Book>

As we can see now, the HTML Tags allows one to describe and control the display of the Address book data. Whereas the XML mark up describes the data elements in an address record. XML Tags are not pre defined. Users can create their own tags for use within their applications to store, transport or exchange data.

XML was created so that richly structured data could be exchanged over the web and other applications. As we stated earlier HTML was too rigid and semantic bound. SGML (Standard Generalized Markup Language) is vendor independent but not suited for exchange of information over the web. XML does not have any predefined tags or structures. In fact in many respects XML can be likened to a meta language that defines the tags and structures used to create a document. XML semantics are generally defined by the applications that process the XML data.

It is important to understand that XML is hardware and software independent. Yes! so is HTML, but XML really does nothing, in the sense, that opening an HTML tagged document in a browser displays the document as designed. For e.g., an element tagged as <BOLD> will be displayed as bold without the <BOLD> tag visible, while an XML document will show up as it is with all the tags showing thus <as Tagged>

Today, XML is used everywhere and it is very difficult to imagine the World Wide Web without XML. XML is one of the most popular tools for exchange of data between various applications. XML was adopted as a web standard on Feb 10 1998 as version 1. The latest version is Version 1, 4th edition, released on 16 August 2006.