The qwertz document types are a set of Standard Generalized
Markup Language (SGML) document type definitions (DTDs) for articles,
reports, books, letters, notes, slides (or overhead transparencies),
bibliographies, and manual pages. Except for manual pages, the
document types have been heavily influenced by the LaTeX document
types of the same names [Lamport86], so LaTeX users should
feel right at home. Indeed, there is a translator, called
format(footnote: format is described in the "Unix Commands"
chapter of this manual.), which converts qwertz
documents into LaTeX and other formats. Anyone familiar with LaTeX
should have no difficulty understanding the LaTeX versions of
documents generated by format; with minor exceptions, only
standard LaTeX commands and environments are used.
So why not just use LaTeX directly, you might ask? Although LaTeX is indeed somewhat of a de facto standard in some scientific circles, it is tied to a particular formatting system, namely TeX. SGML is an ISO standard language for defining the logical structure of documents. There are a number of tools available for editing, parsing and translating SGML documents. SGML structure editors, for example, take advantage of the logical structure of the document being edited to offer functions similar to so-called outline processors, and often use on-screen formatting, similar to WYSIWYG text editors, to eliminate the necessity of typing and viewing the "tags" marking the various regions of text (such as paragraphs, footnotes, and citations). Thus, users need not give up the benefits of an intuitive, easy-to-use editor to acquire the powerful formatting capabilities of systems such as TeX or troff. On the other hand, SGML documents can also be written using any text editor, such as emacs, which many authors may prefer.
Also, the use of SGML provides an amount of independence from
particular formatters. SGML parsers and translators provide the tools
necessary to ease the job of translating documents marked-up in SGML
into any formatting language. It is a relatively painless job to
translate an SGML document into TeX, MS-Word, or troff, for example,
but can be quite difficult to translate documents formatted using one
of these systems into one of the others.(footnote: In fact, format
now is able to generate nroff/troff versions of qwertz documents,
in addition to LaTeX.)
Finally, SGML files can be used for purposes other than printing
documents. In qwertz, for example, we use SGML for
literate programming [Knuth84], extracting and
piecing together the source code of our programs directly from their
documentation. But there are other uses. For example, SGML has been
used in implementations of hypertext and hypermedia.