What Is A Controlled Vocabulary?
http://www.boxesandarrows.com/view/what_is_a_controlled_vocabulary_

Leise, Fred, Karl Fast and Mike Steckel
Boxes and Arrows
2002

Abstract:

A controlled vocabulary is a way to insert an interpretive layer of semantics between the term entered by the user and the underlying database to better represent the original intention of the terms of the user.