The History of XML
Like HTML, XML is a subset of SGML (Standard Generalized Markup Language) and it was designed to address the limitations found in both SGML and HTML. Whereas SGML is a powerful tool that allows documents to be defined in both style and content through Document Type Definitions (DTDs) it remains extremely complex to be used for the World Wide Web and it is unsupported by the commercial Internet Browsers.
On the other hand HTML was designed to be a simple markup language derived from SGML. However, its simplicity also had its limitations especially in terms of form and presentation since HTML has predefined tags. This setback was addressed by the use of Cascading Style Sheets (CSS). Nevertheless, the concept of simplicity in HTML was extremely limiting to website developers with the result that it became way more complicated than it was originally intended.
Furthermore, the style used to render the presentation of web pages defeated the scope of the HTML standard since style sheets where often rendered differently in different browsers, such as Netscape’s and Microsoft’s.
Discussions in relation to a new Extensible Markup Language emerged in 1996 as an attempt to create a new markup language with the versatility and possibilities of SGML while retaining the simplicity of HTML.
The pioneers of XML were a group of people including Jon Bosak from Sun and Tim Bray, who applied their knowledge of SGML to create a new markup language stripped away from the complexities of SGML while retaining its potential to define how a particular document could be structured and identifying its tags through Document Type Definitions.
The result of XML was the possibility to revisit HTML and transmute it into an XML application, better known as XHTML that extended HTML 4 by using XML.