HTML-PRETTY 1 "04 December 1997" "Version 1.00" [section 10 of 14]

PRETTYPRINTER LIMITATIONS

In SGML, this is conventionally done in SGML declaration files for syntax definitions, and in DTD files, which are analogous to LaTeX style files. Low-level typesetting commands of the flavor ``select a 14-point Lucida-BoldItalic font'', ``skip down vertically 6 picas'', and ``draw a horizontal rule 3 ems long'' are notably absent. SGML documents are expected to use only high-level markup commands, leaving the visual appearance entirely up to the DTD specification, and the formatting software.

Unlike LaTeX and TeX, SGML is not a typesetting system. It is only a grammar for a standard markup language, and it is left to SGML software implementors to write DTDs, and to provide for translation of SGML documents to specific document formatting, typesetting, or word processing systems. In this respect, SGML is similar to the RTF (Rich Text Format) supported by many popular word processors, in that it can serve as an intermediate language for electronic document exchange; several language translators between SGML and other text representations are mentioned in the SEE ALSO section below. Regrettably, there is wide variation in the capabilities and document models of current text formatting systems, so such translations are usually rough approximations that may require substantial hand patching to make them truly satisfactory.

HTML is a modest subset of SGML, with tag names apparently chosen from SGML, the Free Software Foundation's TeXinfo system (which in turn is modeled on the earlier Scribe document formatting system), and occasionally, also from LaTeX.

html-pretty is written in this spirit: it knows about the meaning and typical use of all standard HTML tags, but nothing about other SGML DTDs. However, the style-file facility makes it possible to prepare formatting rules for any SGML DTD, extending the applicability of html-pretty to the entire world of SGML, provided a tag normalizer such as sgmlnorm(1) or spam(1) is available to supply omitted tags, and expand abbreviated ones. However, since SGML tag names depend on the specific DTD, and DTDs tend to be proprietary, html-pretty is not packaged with pre-written style files for SGML.

Contributions of suitable style files for public SGML DTDs, together with those DTDs, are hereby solicited, and they may be included in future releases of html-pretty.