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. Membership in this group is free. As well as enabling you to download the UDEF definitions, it will give you access to more information about the UDEF, and allow you to contact other users of the UDEF, and UDEF experts.
The existing UDEF definitions cover many of the basic data element concepts that may be used within an enterprise. If you find that you need additional UDEF definitions, then you can request extensions to the UDEF by sending e-mail to firstname.lastname@example.org. Before doing so, you should read Extending the UDEF. By submitting a request for an extension, you become a Contributor under the UDEF Contribution Agreement, and you agree to the terms of that agreement.
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.