What is it?
XHTML (Extensible Hypertext Markup Language) is a markup
language for web pages that combines HTML with XML. It was intended
to replace HTML, but there is no sign of this happening on a wide
scale yet.
Even so, the World Wide Web Consortium (W3C) is set to approve
XHTML2 next year. This could create an even bigger step, and a
greater range of backward compatibility problems for those who have
ignored XHTML.
It would not be the first time that users have frustrated the
plans of the technocrats by sticking with a popular technology.
But in the case of XHTML, the arguments to switch seem strong,
even if they are often couched in terms that appeal only to a
dedicated minority.
Standardisation means greater device independence, and could
eliminate much of the time wasted checking browser compatibility.
Standardised web pages can be understood by XML-savvy applications,
as well as by people.
XHTML has been described as offering "all the benefits of XML
while avoiding the complications of true XML" - bridging the gap
for HTML developers who might not fancy taking on something as
tricky as full XML.
Where did it originate?
In 1999, the W3C brought out HTML 4.0 and XHTML, which was
essentially HTML 4.0 recast into XML. The W3C said XHTML brought
"the rigour of XML to HTML".
HTML, XML and XHTML all derive from SGML (Standard Generalised
Markup Language). XHTML2 is intended to represent "a complete break
from the non-XML heritage of HTML".
What is it for?
According to Steven Pemberton, chair of the HTML and forms
working groups at the W3C, the design aims of XHTML 2.0 include
using XML as much as possible.
He said, "Where a language feature already exists in XML, do not
duplicate or reinvent it." The emphasis is on structure over
presentation.
"Thanks to Cascading Stylesheets (CSS), you no longer need
explicitly presentational tags in HTML." And by removing some of
the "needless idiosyncracies" of HTML, it should make it easier to
maintain, if not to write.
What makes it special?
Apart from the advantages of standardisation, greater
interoperability will be possible between XHTML and other XML
languages. Semantic web applications will be able to use XHTML
documents.
How difficult is it to master?
HTML developers are said to be able to pick up XHTML in their
spare time in about a week.
What is coming up?
XHTML2 is not likely to become a W3C recommendation until 2007.
In the meantime, acquiring the skills could give you the edge in a
vibrant new jobs market - bearing in mind there may be no immediate
upsurge of XHTML2 work.
According to IBM's Developerworks site, you can prepare by
getting serious about using CSS and removing presentational
mark-up.
Rates of pay
XHTML developers can earn £30,000, rising to £35,000 with more
experience.
Training
You can pay for XHTML training, but there are thousands of free
tutorials. For a proper understanding, start with the W3C site or
look for books by the W3C's HTML/XHTML expert Dave Raggett.
www.w3.org/MarkUp/tutorials
www.w3.org/TR/2005/WD-xhtml2-20050527
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