Design Constraints

When designing the HTML document type, consideration was given to a certain simplicity in order to allow many browsers and hopefully editors to be developed on many platforms.

Lack of nesting

Many text editing systems (Microsoft Word, The NeXT text object, the Mac text object, etc) handle text in a variety of styles but do not have any concept of nestable structure in the SGML sense.

The constraint here is therefore that HTML be able to be mapped into a sequence of paragraphs of styled text, and that if that text is edited that the editor should be able to map the sequence of styles back onto a sequence of elements in a well-defined way. This allows some limited trivial nesting (eg LI within UL) but no general nesting, as a finite and small set of styles is used. In particular, the styles are not parameterized by the nesting level.

(Note: this restriction has been removed., if styles are expressed as functions of the nesting, rather than a selection from a fixed set)

Logical Markup

It is required that HTML be a common language between all platforms. This implies no device-specific markup, or anything which requires control over fonts or colors, for example. This is in keeping with the SGML ideal.

Lack of specific semantics

Just as the markup must not be device-specific