HTML is a subset of SGML - Script/GML is a type of markup used on IBM mainframes to generate formatted documents. It is a sign-style language where one type style is set and stays set until another tag is encountered.
HTML is not a programming language, although it can be viewed as a "glue" that holds together many programming languages, such as JAVA, PERL, and C++. [1]
There are certain constraints that are meant to be followed when using HTML.
This is from the
W3C
statement of direction concerning HTML. [2]
It is part of the
W3C activity list.
Requirements
A simple scaleable document format that can be used for information exchange on virtually any platform:
The document format should be, as far as practical, backwards compatible with existing HTML documents. It should support both paged and scrolling layout models. It should work well with separate style sheets, but not require support for this in browsers. It should support the common needs of information providers for delivering services over the World Wide Web. It should be practical to create HTML documents by directly editing the markup; with wysiwyg editors for HTML; with filters from common word processing formats; and from other SGML document types.
It should work well with separate style sheets, but not require support for this in browsers. It should support the common needs of information providers for delivering services over the World Wide Web. It should be practical to create HTML documents by directly editing the markup; with wysiwyg editors for HTML; with filters from common word processing formats; and from other SGML document types.[2]
The use of HTML has quickly evolved out of the basic tenets that allowed it to happen in the first place. This seems to be mostly facilitated by Netscape writing Web browsers that support HTML that is not in the publicly agreed on specifications. (Being a member of the W3C does not seem to require a company to go by its statement of direction.)
[1]http://scholar.lib.vt.edu/jpowell/htmlplus/chapters/chapter2.htm
HTML Plus! byJames Powell, Virginia Polytechnic Institute & State University
[2]http://www.w3.org/pub/WWW/MarkUp/Activity/
[3]http://www.w3.org/pub/WWW/MarkUp/html-pubtext/