Controlled vocabularies provide a way to organize knowledge for subsequent retrieval. In library and information science controlled vocabulary is a carefully selected list of words and phrases, which are used to tag units of information (document or work) so that they may be more easily retrieved by a search.

The fundamental difference between an ontology and a controlled vocabulary is the level of abstraction and relationships among concept. A formal ontology is a controlled vocabulary expressed in an ontology representation language. This language has a grammar for using vocabulary terms to express something meaningful within a specified domain of interest. The grammar contains formal constraints (e.g., specifies what it means to be a well-formed statement, assertion, query, etc.) on how terms in the ontology’s controlled vocabulary can be used together.

Controlled vocabulary uses in making ontology not only to reduce the duplication of effort involved in building an ontology from scratch by using the existing vocabulary, but also to establish a mechanism for allowing differing vocabularies to be mapped onto the ontology.

Here is the list of famous controlled vocabularies:

  • FOAF: Friend Of A Friend—the most well known vocabulary for modeling people (and one of the most well known RDF vocabularies), FOAF can represent basic person information, such as contact details, and basic relationships, such as who a person knows.
  • SKOS: Simple Knowledge Organization System — it provides a model for expressing the basic structure and content of concept schemes such as thesauri, classification schemes, subject heading lists, taxonomies, folksonomies, and other similar types of controlled vocabulary. Useful for describing models that have some hierarchy and structure but are not sufficiently discrete and formal to map directly into OWL.
  • AIISO: Academic Institution Internal Structure Ontology—effectively models organizational relationships, such as Institution->School->Department->Faculty with the property part_of and defines courses taught by those Departments with the teaches property. AIISO was developed within the past year by Talis, a software company dedicated to semantic technologies, for their academic resource list management system, Talis Aspire.
  • University Ontology—University ontology is undergoing active development and is currently unstable, but does a good job of modeling the details of course scheduling. It is being developed by Patrick Murray-John at University of Mary Washington, who is in touch with the developers of the AIISO ontology at Talis.
  • SWRC: Semantic Web for Research Communities—there is much overlap between AIISO and SWRC. While there is a text on the development of SWRC, it is hard to find a clear documentation of the ontology itself, so a comparison of the two would take more time.
  • DC: Dublin Core—One of the original and most widely used vocabularies, Dublin Core can be used for cataloging publications.
  • bibTeX.owl—bibTeX is a format description for source citation. bibTeX.owl is the bibTeX ontology chosen by Nick Matsakis to use in his BibTeX RDFizer that is part of MIT’s SIMILE project. Depending on whether bibTeX data is prevalent and used throughout the community, this may be another option for cataloging publications.
  • Bibliography ontology—Bibliography reuses many existing ontologies such as Dublin Core and FOAF properties. It’s goal is to be a superset of legacy formats like BibTeX. It has multiple levels, such as level one which is for simple bibliographic data, or level three which can aggregate many medium sources like: writings, speeches, and conferences. It is used in the University ontology.
  • SIOC:Semantically-Interlinked Online Communities—SIOC Core Ontology Specification – an RDFS/OWL vocabulary/ontology for describing the main concepts and properties for online communities.