What's So Cool about DHTML?
For the moment, ignore the competing
visions for DHTML and just try to get the basic concepts straight. This not
only helps you understand what the fuss is all about, but it should also help
you appreciate why DHTML really is pretty important, and what kind of impact
DHTML could have on the Web in general, and maybe even on your own Web pages.
The essence of DHTML is this: Instead
of transferring and creating static HTML-based documents on the client side
of a Web connection, DHTML makes it possible to transfer a document description
to the client side that can be changed in specific ways once it gets to the
client, by activating associated scripts to rewrite the HTML and redisplay
it (the Microsoft way) or by setting up different views of information on
multiple layers in a document, and then switching between layers to change
from one view to another (the Netscape way).
DHTML may not sound too exciting
in the abstract, so to get a little more specific, we discuss what this can
do for a Web page:
DHTML creates terrific support for hierarchical
menus, in which clicking a selection on one menu causes another
submenu to pop up (in other words, this lets Web designers create
a user interface thats familiar to anyone whos used
a GUI application like MS Word, a Web browser, and so on).
The ability to change the page on the
client side, in response to user selections (no matter how its
handled), means that users can interact with Web documents much
more quickly, because they dont have to issue a request for
a new page to the server across the Internet and wait for that page
to arrive. DHTML enables Web page designers to package everything
needed to support interactivity in a single document and send that
document to users all at once, instead of a little bit at a time.
That helps explain why some experts say that DHTML may replace the
current Web site architecture, which consists of lots of simple,
static HTML documents, with many fewer, but much more complex, dynamic
Because HTML supports style sheets
(CSS1 and CSS2), and DHTML can operate on style sheets as well as
HTML documents, page designers can even change styles dynamically.
Font selections, sizes, and text color can all change in response
to user actions on a Web page. For example, the contents of a Web
site map could be presented in 4 or 5 point black type to allow
as much information as possible to fit on a single screen, but whichever
item the user selects for examination could be presented in more
readable 8 or 9 point type, with multiple colors. DHTML can even
reflow the other text around whatever the new focus might be to
make it appear as the current center of attention. The
possibilities for this kind of dynamic handling for whatever becomes
the users focus in a document are limitless and magical.
Microsoft announced in 1996 that it
would switch its Windows Help environment from a proprietary implementation
to HTML. Because of the need for access to help topic indexes, multiple
displays, and precise positioning of elements on screen, DHTML is
an ideal technology to use for building help systems. As an added
bonus, such documents would work equally well from a CD-ROM, a hard
disk, or across the Web.
really could go on (and on and on) here, but we hope this gives you an idea
of the extraordinary power and potential inherent in DHTML! In the sections
that follow, we take a closer look at Microsofts and Netscape
ideas on this fascinating subject, and then show you how the W3C is trying
to create a standard out of these powerful, but incompatible, visions.
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Revised -- January 16, 1998