The Universal Data Element Framework (UDEF) was [1] a controlled vocabulary developed by The Open Group.
It provided a framework for categorizing, naming, and indexing data.
For example, an "employee number" is often used in human resource management.
It has a UDEF tag a.5_12.35.8 and a controlled vocabulary description "Employee.PERSON_Employer.Assigned.IDENTIFIER".
UDEF has been superseded by the Open Data Element Framework (ODEF).