A TEX macro package with the properties of a Generalized Mark-up Language
has already been developed.
It is called LaTeX.
With LaTeX the author uses `generalized mark-up' commands such as
`\title', `\begin{abstract}', `\section',
`\appendix', which bear no relation to a particular typographical
format at all.
The typographical format of the final printed copy of a LaTeX manuscript
is determined by so-called `style files'.
LaTeX comes with four standard style files, which allow the user to
produce typographically sound articles (papers), books, reports, and letters.
But these style files may be replaced by others, to produce an entirely
different typographical format of a document from the same
mark-up commands.
Thus, if a publisher accepts the source text of a LaTeX manuscript, he
can convert it into printed output with almost any desired
typographical format,
without changing the original text.