You can download the UDEF definitions, in XML or in RDF format, for use in your enterprise. To do this, you must join the UDEF Interested Parties Group.
Files for versions 1.12 and later can be retrieved from directories http://www.opengroup.org/udefinfo/dl/Vx/ where x is the version id. For example, the files for version 1.2 are at http://www.opengroup.org/udefinfo/dl/V1.2/.
A history file describing the versions of the UDEF to date, and showing which files have changed for each version, is at http://www.opengroup.org/udefinfo/dl/UDEFHistory.xml.