Subject: HTML Standards, Dynamic HTML and all that
Often, while designing HTML pages (or Web pages), one checks for the final
effect (on-the-screen appearence) with one's favorite browser. But one may
find that on a different browser or on a different platform the colours or
the tables are rendered in a totally different way. At least, I came across
this a couple of times in my limited Web authoring experience.
Or
you may be browsing the Web and come across a Web page that is displayed
unintelligibly on your screen. The reason could very much be that the
author of this unintelligble page used a browser different from yours and
was satisfied with the way it renders the page in question.
Each browser of late has its own standards for HTML, with an extra tag or
two of its own, while all the time W3C (W3 Consortium) strives to bring
out new standards of HTML!
While giving an overview of the main developments in the lingua-franca of
the Web (HTML), Agnes Tatarka in the following article says, "many Web
authors are not exploiting some of the enhanced functionality that these
new developments offer."
Hope those of you who use HTML for Internet/Intranet purpose would find
it useful.
- Ravi
ravi@ncsi.iisc.ac.in
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Beyond
: Developments in HTML
Agnes Tatarka, Information Technologies, Network Solutions,
Inc.
Not long ago, in geologic time, I gave several presentations
covering the basics of Web authoring. I assured my audience
that, armed with a text editor and the knowledge of how to use
six HTML tags, they too could be Web authors. In the intervening
years, expectations of what Web pages should (or could) look
like has changed, expectations of what Web pages can do has
changed, and HTML has evolved to try and meet some of those
demands. What follows is an overview of the main developments
that have or are taking place in the language of the Web -
HTML.
HTML Standards
We all know what HTML is, right? The Hypertext Markup
Language (HTML) is a specific application of the Standard
Generalized Markup Language (SGML), a system for defining and
using document formats. The World Wide Web Consortium (W3C), the
group responsible for standardizing Web-related technology,
published the current standard, HTML 3.2 Reference Specification
(http://www.w3.org/TR/REC-html32.htmlrelease/nw97-96a.htm.htmladeffects.html), on January 14, 1997. Its
goal was "to capture recommended practice as of early 1996"
Browser developers had, of course, deployed new versions of
their software that defined new tags or expanded what one could
do with the tags defined in the 3.2 specification. Again the
standards writers sought to catch up, publishing the HTML 4.0
'Working Draft' on July 8, 1997. (A Working Draft precedes a
Recommendation and, as its name suggests, is subject to change.)
It is expected that HTML 4.0 will gain the status of a
Recommendation in late 1997 or early 1998.
Changes in HTML 4.0, in its current iteration, over the current
standard include:
* eight new tags (referred to as elements in the Working
Draft);
* ten deprecated (supported but not encouraged) tags
including and ;
* changes to tables that improve presentation and control for
example aligning on periods or commas;
* enhancements to forms that would allow buttons in addition
to the current "submit" and "reset" and field value
checking before the form is submitted;
* support of style sheets, including support of a range of
style sheets languages.
A summary of the changes between 3.2 and 4.0 can be found at:
http://www.w3.org/TR/WD-html40-970708/appendix/changes.htmlmladeffects.html
Style Sheets
The authors of HTML: The Definitive Guide, Second
Edition (http://www.ora.com/catalog/html2/0708/appendix/changes.htmlmladeffects.html) caution
their readers to be aware of HTML's limits. The fundamental rule
that aspiring Web authors must yield to is: "HTML is designed to
structure documents and make their content more accessible, not
to format documents for display." Web authors are familiar with
the amount of coding required to simply associate a font face,
size and color to parts of a document - every instance must be
tagged separately. To control layout many Web authors have
resorted to using combinations of transparent gifs, tables, and
HTML tags like . While the sought-after effect can
be achieved, the same page on a different browser, on a
different platform, with different set of user-set options, will
probably not look like what they have so laboriously laid out.
These pages also often suffer from being incomprehensible for
those relying on text-based systems or screen-readers.
Those of us who come to the Web with a desktop publishing
background (or even those who take the time to learn a good
word processing program) are familiar with style sheets. Define
the fonts, leading, size, and margins once and apply it to the
appropriate pages or parts of a document. If you decide to
change the font color- do it once and you are done. Anyone who
has contemplated redesigning her Web site or gone through a
protracted design phase knows that such functionality in Web
page design is long overdue. Style sheets could also be used for
customizing the layout for a variety of devices - TV, Personal
Digital Assistants, and screen readers.
Status of Style Sheets
The first W3C proposal for style sheets came out as early as
October 1995. In December 1996, Cascading Style Sheets (CSS1)
became a W3C Recommendation. "Cascading" refers to the fact that
there are rules of precedence in CSS. Simply put, the style that
is "closest" to the tag will override styles that are evoked at
a higher level. The W3C now has a separate working group on
Cascading Style Sheets and Formatting Properties to address some
of the needs of designers and developers. While neither of the
two major browsers support the full CSS1 specification, Internet
Explorer 3.0 and version 4.x of both Internet Explorer and
Netscape Navigator provide some (but different) support for
CSS1. Web authors will need to be aware of the different
implementations. WebReview maintains a Browser Compatibility
chart at http://www.webreview.com/guides/style/mastergrid.htmls.htmlmladeffects.html
and Microsoft details Internet Explorer's support at
http://www.microsoft.com/workshop/author/css/css-ie4-f.htm.mladeffects.html
There are currently three CSS-related Working Drafts covering
positioning, printing and aural output. One of the most exciting
is the "Positioning HTML Elements with Cascading Style Sheets"
(http://www.w3.org/TR/WD-positioninguthor/css/css-ie4-f.htm.mladeffects.html) W3C Working Draft of
January 31, 1997. Imagine no more transparent gifs and "table
magic" to control what the page looks like. Imagine not spending
hours creating a complex layout, all the while knowing that the
same page on a different browser, on a different platform, with
a different set of user-set options, will probably not look like
what you so carefully designed.
How they work
Style sheets can be applied be applied in three ways:
* use inline styles to associate style properties and their
values for a particular tag. This approach would be used to
override any other style sheets associated with the
document.
* use document-level styles to define and associate a style
with all tags within a document. This would override any
external style sheet properties.
* use external style sheets to define a style and its
properties. This approach exploits the real power of style
sheets by allowing updates across an entire collection.
Dynamic HTML (DHTML)
You've seen the headlines, the books are starting to show up on
the bookstore shelves, and the FAQs and Web sites dedicated to
Dynamic HTML (DHTML) are a click away. But what exactly is
DHTML? According to the folks at W3C who published the Document
Object Mode (DOM) upon which the promise of DHTML hinges,
"'Dynamic HTML' is a term used by some vendors to describe the
combination of HTML, style sheets and scripts that allows
documents to be animated" (http://www.w3c.org/DOM/-positioninguthor/css/css-ie4-f.htm.mladeffects.html).
Yes, we've all seen the tricks with an image changing on a
mouse-over. What the DOM does is extend the ability to use
client-side scripting (JavaScript, VBScript, e.g.) or other
applications against all of the page's elements in an HTML
document, including style sheets. Triggered by a user action
(moving a mouse over a given element) or a timed event, both
content and look can be changed on the fly.
Status of Document Object Mode
The DOM Specification was released to the public as a Working
Draft on October 9, 1997 and at present only includes what is
called Core Level 1. Work is in progress on other parts of the
Specification.
Both Microsoft Internet Explorer 4.0 and Netscape Communicator
browsers support DHTML, but in quite different ways. One of the
major differences in the implementations is Netscape's use of
the tag and reliance on JavaScript Style Sheets (JSSS),
although they do support CSS. The implementations also support
different event handling models. Events are actions such as
clicking on a hyperlink, or loading an image. The event handling
model describes how that event is connected to a script action
as well as "which events can be detected, and the syntax for
capturing, handling, and working those events" (Nick Heinle,
"Dynamic HMTL and the New Event Models,"
http://www.dhtmlzone.com/articles/eventmodels.htmie4-f.htm.mladeffects.html).
The most compelling feature of Microsoft's implementation is
called Current Record Binding - the ability to merge data from a
data source object (a comma delimited file or database) and
display them as page elements.
Beyond HTML
Even with all these developments and enhancements to HTML,
problems with inconsistent browser support and the limits of
HTML, prompted WC3 to start a working group on the Extensible
Markup Language (XML). Unlike HTML, XML is not a markup language
in the sense that it defines a set of tags or elements. Rather
the goal of XML is to provide the Web publisher with the ability
to write customized markup tags based on the demands of the
information they are working with. For instance, Microsoft's
Content Definition Format (CDF) is based on XML.
Status of Extensible Markup Language
WC3 issued a Working Draft for XML in August 1997. A
Recommendation is expected to be published this year. An
excellent XML FAQ is available at http://www.ucc.ie/xml/om/articles/eventmodels.htmie4-f.htm.mladeffects.html
Conclusion
Given the disparity between the current standard and what the
commonly-used browsers support, it is often the case that the
specifications for a Web design project will reference not the
HTML version but rather the most widely-used versions of the two
major browsers: Netscape Navigator and Micorsoft Internet
Explorer. Current practice, from my experience, is to design to
version 3.x of both browsers and a log file analysis for the
InterNIC site supports this approach.
What this means is that many Web authors are not exploiting some
of the enhanced functionality that these new developments
offer. If they are like me, they yearn for style sheets, keep
their eye on the browser wars and the latest from the W3C, and
sometimes harken back to the days when six tags were enough.
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