single-source publishing—one source document, many target output formats
print output (PostScript, PDF, RTF, OOXML, ODF)
Web output (HTML/XHTML, single page, chunked output)
help systems (HTMLHelp, info, man, JavaHelp, Eclipse help)
other formats (ePub, LaTeX, ConTeXt)
publishing chain can be fully automated and handle frequent changes in a documentation
modular documents—content reuse
conditional documents
authors no longer have to worry about presentation