XKB - X Keyboard Extension
The XKB data files for the various keyboard models, layouts, and locales are now maintained by the X Keyboard Config project on freedesktop.org
some helpful links:
Patch XKB to support more than 128 keys: http://planet.gentoo.org/developers/flameeyes/2005/06/15/and_the_keyboard_lose_the_match
RMLVO keyboard configuration (rules, models, layouts, variants and options)
The original XKB extension protocol and library specs are available in several formats:
Original XKB specifications in FrameMaker format, as previously found in the xorg-docs module in git
Original XKB specifications from X11R6.4 in PostScript & PDF
XKB libX11 API documentation in HTML, generated from current DocBook sources
XKB protocol specification in HTML, generated from current DocBook sources
XKB libX11 API documentation in PDF 1.4, generated from current DocBook sources
XKB protocol specification in PDF 1.4, generated from current DocBook sources