XML stands for Extensible Markup Language. It was designed to allow the carrying of data that can then be universally processed by any application that supports it. With XML, tags are not predefined so the user can create their own set of tags unlike HTML.

XML supports Unicode, which allows us to store almost any information, in any written human language. XML was born in February of 1998 as a W3C recommendation to resolve the issue of storing and transporting data across multiple platforms on the web.

XML and HTML appear to de identical, except that each were designed with different goals in mind. XML was designed to transport and store data with the focus on what the data is, were as HTML was designed to display data with the focus on how the data looks.

XML is essentially plain text. If opened in a standard text editor, the structure and data stored is usually simple enough for a human to read, as XML was designed in this way. When opened in an XML-aware application, data can be extracted and processed according to the applications specification, just as HTML is processed in a browser to display its data as a webpage.

It’s amazing how quickly XML has taken off, so much so that a large number of software vendors have adopted the standard and use it as their main method of data storage/transfer. One of the biggest uses of XML today is on shopping feeds; companies like Google and Shopping.com all accept XML files to import data for their online shopping portals.

XML has carved the way for a number of other technologies such as XHTML, xPath and xQuery. These are all based on XML, in that some are used to process XML and others take the advantages of XML to apply to themselves.

XML is a simple yet vast subject, which will come up time and time again as its usage increases. In the near future we will see the release of XHTML 5 which boasts a number of extra features over current versions and also takes more advantages of XML with its use of custom tags.