What are the ontologies that are fully documented, used by various datasets, and supported by tools

I would like to establish a list of ontologies/vocabularies that match the following criteria:

  • they are fully documented, that is, there exists a documentation online that describe the ontology itself and all the terms it defines (provide a link to the documentation);
  • they are used by at least 2 independent datasets (please provide a derefencable link to the datasets as a proof);
  • they are supported by tools (give examples or a link to the tools or to a list of tools);
  • additionally, you can provide a link to a project webpage;
  • you can also give technical details about the ontology, such as the number of classes it define, etc.

Please, I would like you to provide separate answers for each ontology/vocabulary you mention so that people can vote individually for an ontology.

Edit: I put here for convenience direct links to the ontologies given in the answers, in order of appearance.

Vocabulary of Interlinked Datasets (voiD)

Description: a vocabulary and a set of instructions that enables the discovery and usage of linked datasets.

Project homepage: http://vocab.deri.ie/void

Namespace: http://rdfs.org/ns/void#

Typical prefix: void:

Documentation: http://vocab.deri.ie/void/guide

Which datasets use it: Fairly widely deployed; some examples include:

Tools supporting it:

Technicalities: Lightweight RDFS vocabulary containing 3 classes and 13 properties. voiD vocabulary directly re-uses terms from scovo: and dctypes: namespaces, and recommends use alongside FOAF and DC(Terms) for describing datasets.


Semantically Interlinked Online Communities (SIOC) ontology

Description: this ontology is used to describe online communities such as forums, blogs, mailing lists, wikis. It complements FOAF by stressing on the description of the products of those communities (posts, replies, threads, etc).

Project homepage: http://sioc-project.org/

Namespace: http://rdfs.org/sioc/ns#

Typical prefix: sioc:

Documentation: http://rdfs.org/sioc/spec/

Which datasets use it: SIOC is used on many different websites. Notable examples are: identi.ca (http://identi.ca/danbri/foaf) or CC car pictures (http://carpictures.cc/cars/photo/index.rdf). See also a list of (mostly broken) links to sites using SIOC.

Tools supporting it: most notably, Wordpress and Drupal have a module supporting it. There is a page that references many applications using SIOC.

Technicalities: SIOC is a lightweight ontology (17 classes, 61 object properties, 25 datatype properties). It is essentially in OWL 2 DL, with tiny syntactical issues that strictly speaking makes it a non DL ontology. It only relies on OWL 2 RL constructs. There exists other "subvocabularies" for SIOC with domain names http://rdfs.org/sioc/xxxx# but I am not aware whether these ones are used or supported.

Simple Knowledge Organization System (SKOS)

Description: a W3C standard ontology for describing thesauri, taxonomies, and other controlled vocabularies.

Project homepage: http://www.w3.org/2004/02/skos/

Namespace: http://www.w3.org/2004/02/skos/core#

Typical prefix: skos:

Documentation: http://www.w3.org/TR/2009/REC-skos-reference-20090818/

Which datasets use it: Library of Congress and New York Times subject headers, United Nations Food and Agriculture Organization's AGROVOC thesaurus, NASA, IPTC, lots more. See http://www.w3.org/2001/sw/wiki/SKOS/Datasets.

Tools supporting it: TopQuadrant's EVN, PoolParty, SKOSed plugin for Protege,iQvoc, TemaTres