HTML and CSS Reference
In-Depth Information
distance it from the tawdry reputation of
DHTML
despite being mostly
the same thing. Although the web had long been touted as a platform
for applications, the
AJAX
trend looked like it had a chance of making
that possibility a reality.
The competing standards
You may have wondered what the
W3C
has been doing in the decade
since
HTML 4.01
was released. It has, of course, been working on
plenty of standards other than
HTML
, but it's also working on a
replacement for
HTML4
. The
W3C
decided that the future of
HTML
lay in
XML
.
XML
is superficially similar to
HTML
—documents, tags,
and elements all exist in
XML
, but it has two major differences:
XML
parsing is much stricter than
HTML
.
A few mistakes in an
HTML
document will, in many cases, not even be noticed; the browser will
correct the errors as best it can and carry on. A single error in an
XML
document causes the parsing to fail and an error message to be
displayed. The stricter approach allows browsers to be more effi-
cient, which is particularly useful on mobile and low-power devices.
❂
XML
is extensible.
If you want to add new elements to your
XML
page, you can do so. You describe those elements in a separate file
and link to it from your document. Your new elements are then just
as valid as any specified by the
W3C
.
❂
The first step was to redefine
HTML 4.01
as an
XML
standard.
XHTML 1.0
became a Candidate Recommendation in October 2000. It
contained no new elements or features; all the valid elements were
identical to those in
HTML 4.01
. The only changes came from it now
being a dialect of
XML
. The plan was to extend
XHTML
in a modular
fashion by plugging in new
XML
dialects. Some of the better-known
XML
dialects the
W3C
expected to be plugged in to
XHTML
were
Scalable Vector Graphics
(SVG)
, which became a
CR
in August 2000;
and
M
ath
ML
, an
XML
language for describing equations, which
became a
CR
in April 1998. The modular approach allowed different
technologies to be worked on at different paces.
