TMML is an XML DTD designed for the documentation of Tcl, Tk, and other Tcl extensions.

See  http://www.hwaci.com/sw/tcldoc/beta2.tar.gz for the
second public beta release of the XML sources for the core Tcl/Tk
documentation.  http://www.hwaci.com/sw/tcldoc/html/ is the web
site which discusses more about the effort.  Also, see
 http://www.hwaci.com/sw/tcldoc/html/ for web based versions of
the Tcl and Tk man pages.  Some more up to date work on this effort has
been put on  http://tmml.sourceforge.net/ .