Guide Template on Ontologies and Controlled Vocabularies

Ontologies vs. Controlled Vocabularies

A formal specification of a vocabulary (a "controlled vocabulary") can be found as a plain list of words, a dictionary, a taxonomy, an Entity-Relational (ER) diagram, an Object Model in Unified Modeling Language (UML) diagram, an eXtensible Markup Language (XML) schema and possibly many others. A controlled vocabulary can also be an ontology when the concepts are defined explicitly by creating classes. A class is created using a mental abstraction or concept, which can be a classification, an aggregation or a generalization [Batini, 1992]. For example, a list of terms such as USA, Germany, and Colombia do not represent any explicit conceptual relation until an explicit class Country is abstracted to classify them.

In addition to this requirement an ontology needs to conform to strict hierarchical subclass relationships between the classes [Gruber, 1993]. Also, in ontologies, the classes have instances (individual members of the class), properties, and relationships among them.

It should be noted that these terms (in particular 'ontology') have been defined many different ways in different publications. Deborah McGuinness, for example, has proposed that an ontology could be construed as including the entire spectrum of controlled vocabularies. We have documented in this FAQ one of the more common discriminators, but other papers and usage may vary.


C. Batini, S. Ceri and S.B. Navathe, Conceptual Database Design, The Benjamin/Cummings publishing Company, Inc., Redwood City, California, 1992.

T. Gruber, A Translation Approach to Portable Ontology Specification., Knowledge Acquisition 5(2), 199-220, 1993.

Examples of Ontologies and Controlled Vocabularies Relevant to Our Domain(s) of Interest

examples (link to ontologies of interest here)