The Document Object Model (DOM) is a tree structure that represents the page internally in applications, and XHTML and HTML are two different ways of representing that in markup (serializations).
Both are less expressive than the DOM (for example, "--" may be placed in comments in the DOM, but cannot be represented in a comment in either XHTML or HTML), and generally XHTML's XML syntax is a little more expressive than HTML (for example, arbitrary namespaces are not allowed in HTML).
By February 1999 the name of the specification had changed to XHTML 1.0: The Extensible Hyper Text Markup Language, and in January 2000 it was officially adopted as a W3C Recommendation.
Modularization provides an abstract collection of components through which XHTML can be subsetted and extended.
while at the same time updating the HTML specifications to address issues raised in the past few years." Ian Hickson, editor of the HTML5 specification criticising the improper use of XHTML in 2002, December 1998 saw the publication of a W3C Working Draft entitled Reformulating HTML in XML.
This introduced Voyager, the codename for a new markup language based on HTML 4, but adhering to the stricter syntax rules of XML.
By migrating to XHTML today, content developers can enter the XML world with all of its attendant benefits, while still remaining confident in their content's backward and future compatibility." However, in 2005, the Web Hypertext Application Technology Working Group (WHATWG) formed, independently of the W3C, to work on advancing ordinary HTML not based on XHTML.With XHTML 1.1, it is one of the two first implementations of modular XHTML.In addition to the Core Modules (Structure, Text, Hypertext, and List), it implements the following abstract modules: Base, Basic Forms, Basic Tables, Image, Link, Metainformation, Object, Style Sheet, and Target.The standard known as XHTML5 is being developed as an XML adaptation of the HTML5 specification.The World Wide Web Consortium (W3C) also continues to maintain the HTML 4.01 Recommendation, and the specifications for HTML5 and XHTML5 are being actively developed.