"All MySQL documentation, even the manual pages, internal help tables, and all of the various formats we generate, come from a single source using the standard DocBook XML format. Every destination format but one (CHM) are then built using open source tools. Using a single source for all of this information is obviously a massive benefit, but it is not entirely without its own problems. DocBook XML is great, but there are certain areas where we have had to tweak the format and work around bugs. When it comes to outputting information in specific formats, there are even more issues to consider."

from http://www.freesoftwaremagazine.com/node/1653