docbook is probably the most widely used XML Document Management system

• One source DTD. Example instance:

  <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook V3.1//EN">
  <book>
  <bookinfo>
    <title>My First Book</title>
    <author><firstname>Jane</firstname><surname>Doe</surname></author>
    <copyright><year>1998</year><holder>Jane Doe</holder></copyright>
  </bookinfo>
  <preface><title>Foreword</title> ... </preface>
  <chapter> ... </chapter>
  <chapter> ... </chapter>
  <chapter> ... </chapter>
  <appendix> ... </appendix>
  <appendix> ... </appendix>
  <index> ... </index>
  </book>

• Many XSLT stylesheets for:
  • Formatting for print publication (heavily used by O'reily publishers): PS, PDF output
  • Formatting for Web sites: HTML, XHTML
  • Formatting for computer documentation (GNOME, FreeBSD, PHP, etc.)
  • Formatting slides
  • Documenting code
  • Formal specifications
  • Theses/dissertations
  • and so on...