(This is not an MIT SIPB graphic.)
(This is not an MIT SIPB graphic.)
The SIPB webmasters are often asked "Why don't you use any of the "cool" Netscape tags on your pages?" The answer is because HTML standards exist and we support them. In the case of many of the "cool" tags that the Netscape browser understands, they not part of the HTML standard, as defined in RFC 1866.
Some of the early Netscape tags were in direct conflict with the design of SGML. As RFC 1866 clearly states:
HTML is an application of ISO 8879:1986 -- Standard Generalized Markup Language (SGML). SGML is a system for defining structured document types and markup languages to represent instances of those document types [SGML].
From the SGML page at the World Wide Web Consortium:
"Truth be told, SGML is a well-guarded secret; it is an official International Standard (ISO/IEC 8879:1986) for the electronic interchange of information that has been adopted by the European Community, the governments of the US and Canada, the aerospace, automotive, semiconductor, defense and other industries. But somehow, despite all this acceptance, it remains one of the quietest revolutions around. Granted, it used to have a reputation as being somewhat complicated, but the success of HTML -- which is in fact a simple application of SGML -- shows that anyone can play."
SGML, which stands for "Standard Generalized Markup Language," is not a specific markup language, but a format for implementing markup languages. SGML is hierarchical, and each markup has a starting and ending tag. In HTML, starting tags are of the form <tag> and ending tags are of the form </tag>. Most of these markups can be nested, and every piece of text in a doucment is part of some markup entity. (Running text, for example, is part of a paragraph, for which HTML uses the markup <p>.) If you view the source of this document, you will notice that each paragraph starts with <p> and ends with </p>. Even though HTML assumes text is part of a paragraph by default, this was done to ensure that the document is also a good SGML document.
There is a methodology in SGML for defining tags and attributes, which Netscape does not follow. For example, centering is an alignment attribute, which could theoretically be assigned to several different markups. Thus the SGML-compliant way to describe centered running text would be to start with <p align="center"> and end with </p>. Using this paradigm, the alignment attributes of "left," "center," and "right" could be assigned to several different markups, in a similar manner to the way "top," "middle," and "bottom" are used in HTML 2.0. Netscape's behavior has created problems for the World Wide Web Consortium in filing drafts with the IETF for extensions to HTML.
The World Wide Web Consortium wants to keep HTML as SGML-compliant as possible. This makes sense, since HTML is, after all, an application of SGML. It's also a good idea, both because it makes the language easier to learn, and because it keeps the language compatible with existing and future SGML tools, such as HaLSoft's HTML Check Toolkit.
But even if you already know HTML and never plan to use any SGML tools, imagine what would happen if one or two, or perhaps ten or twenty browsers all became as popular as Netscape, and each ended up with about an equal amount of market share. Then imagine if in order to be able to decipher the various tags in the different documents, you had to use the Netscape browser to read some of the pages, the AOL browser to read others, the Windows95 browser to read still others, MacWeb to read a bunch, and Arena, Viola, HotJava, Chimera, Lynx, or Emacs-W3 to read the rest. Imagine having to exit one browser and start up another one each time you visited a new link!
HTML 3.0 has expired. It was an internet draft, and since it was not renewed, it expired on September 28, 1995. Keep this in mind when you see a web page that claims to be "HTML 3.0 compliant." Here's a copy of the beginning of the HTML 3.0 draft (which has been deleted from the internic site). (It has been reformatted so that it does not scroll off the edge of the screen in most browsers, but none of the text has been changed.)
HTML 3.0 28th March 1995
INTERNET DRAFT Dave Raggett, W3C
Expires in six months email: <dsr@w3.org>
HyperText Markup Language Specification Version 3.0
<draft-ietf-html-specv3-00.txt>
Status of this Memo
This document is an Internet draft. Internet drafts are
working documents of the Internet Engineering Task Force
(IETF), its areas and its working groups. Note that other
groups may also distribute working information as
Internet drafts.
Internet Drafts are draft documents valid for a maximum
of six months and can be updated, replaced or obsoleted
by other documents at any time. It is inappropriate to
use Internet drafts as reference material or to cite them
as other than as "work in progress".
Note particularly the last sentence, since it has rung true in this instance. The World Wide Web Consortium has abandoned HTML 3.0 as a package, and instead decided to submit extensions to HTML 2.0 in pieces.
The following Internet Drafts relating to HTML were on file as of the last update of this document. However, in light of the above comment, please note that they may be obsoleted or retracted without notice. (If that happens, the associated links will cease to work.)
If you decide to start using these extensions and protocols before they are are adopted as standards, remember the above caveats about internet drafts, and don't get too upset if the drafts expire and you're left with a set of useless documents.
Netscape Communications Corporation recently tried to buy advertising on our server and to convince us to use their nonstandard "enhancements" by offering our webmasters six T-shirts. I'm sure you can guess what our answer was...
