XML refers to Extensible Mark-up Language and it is a mark-up language designed for carrying as well as showing data or info through the internet, in a constant and as intended fashion regardless of the systems or internet browsers being used. Hence XML is completely system independent and it is accessible freely.
XML was actually designed to precede SGML and HTML, each of which are also mark-up languages however had their very own boundaries not to mention constraints. For example, SGML was in fact extremely intricate and pricey, this made it hard to use for the web, especially because it was not being maintained by any of the commercial web browsers.
With regards to HTML, despite being for free and also generally supported, it had a number of important problems making it unsuitable for use carrying data via the internet.
Thus XML was designed out of SGML by a team of IT experts from IBM and Sun, who took the best parts of SGML and cut out the unused, complicated and awkward parts. The outcome became a simple, extensible and open specification that was only 26 pages long, in comparison to in excess of 500 pages that the SGML specification came with.
So that’s the basic history v XML, let’s right now have a quick look at what exactly XML is and what it looks like.
In relation to its code syntax, XML is similar to HTML, i.e. you have an opening tag that looks like <xml>, and a closing tag that looks like </xml>
With the exception of the opening and closing tags, the rest of an xml file is merely pairs of opening and closing tags with data (together, the tags and data are known as XML Elements).
Having given a concise history on XML and taking a glance at just what it looks like, lets now dive straight to the advantages and disadvantages, beginning of course with the pros.
The first and clearest benefit is that as opposed to HTML, XML tags do not have semantic meaning; which means that you’re not tied in to using limited tags, for instance, in HTML you have to use the body tag to put your body elements or the head tag to place the head elements.
With XML you really create your own tags suitable for you and you can place whatever you like in between your tags, there are no restrictions within the rules e.g. with HTML only body elements may go within the body tag.
Another benefit would be that along with tags, you can even create and also write your own rules, and these rules, as opposed to HTML, don't have to be restricted to formatting rules, XML permits you to define all types of tags with all kinds of rules, for instance tags representing business rules or tags representing data description or data relationships.
In spite of the many advantages, there is also one significant negative aspect that's prevented XML staying more substantially used than it is at present, which would be the absence of adequate processing programs.
With HTML for instance, you could utilize just about any internet browser to read any HTML document that's not the case with XML, since there are presently no XML browsers available. As a result XML documents should be changed into HTML before you distribute them or even to utilize a middleware program to convert it on the fly.
A far more thorough account of XML can be found in this xml tutorial, http://www.liquid-technologies.com.xml.aspx
, or you can visit the W3C website to learn more.