SKOS

Please refer to the errata for this document, which may include some normative corrections. This document defines the Simple Knowledge Organization System (SKOS), a common data model for sharing and linking knowledge organization systems via the Web. Many knowledge organization systems, such as thesauri, taxonomies, classification schemes and subject heading systems, share a similar structure, and are used in similar applications. SKOS captures much of this similarity and makes it explicit, to enable data and technology sharing across diverse applications. The SKOS data model provides a standard, low-cost migration path for porting existing knowledge organization systems to the Semantic Web. SKOS also provides a lightweight, intuitive language for developing and sharing new knowledge organization systems. It may be used on its own, or in combination with formal knowledge representation languages such as the Web Ontology language (OWL). This document is the normative specification of the Simple Knowledge Organization System. It is intended for readers who are involved in the design and implementation of information systems, and who already have a good understanding of Semantic Web technology, especially RDF and OWL. Using SKOS, concepts can be identified using URIs, labeled with lexical strings in one or more natural languages, assigned notations (lexical codes), documented with various types of note, linked to other concepts and organized into informal hierarchies and association networks, aggregated into concept schemes , grouped into labeled and/or ordered collections , and mapped to concepts in other schemes. This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at This document is a W3C Recommendation developed by the Semantic Web Deployment Working Group , part of the W3C Semantic Web Activity . This document reflects an editorial change arising during the Proposed Recommendation review: a non-normative example and preceding text was removed that suggested one means to reference a system of notation (e.g. a symbolic notation) in a label where the system of notation does not correspond to a natural language. This suggestion was deemed inconsistent with IETF Best Current Practice 47 on the use of tags for identifying languages. Users should consider the SKOS Extension vocabulary for support of alternate systems of notation. An implementation report documents known uses of SKOS during the Candidate Recommendation review period. An updated SKOS Primer is being published concurrently with this Recommendation. Removed final paragraph and example from section 6.5.4 on use of private use language sub-tags. Editorial changes to references section and citation of SKOS Primer. This document was produced by a group operating under the 5 February 2004 W3C Patent Policy . W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy . Appendix A. SKOS Properties and Classes A.1. Classes in the SKOS Data Model Appendix B. SKOS eXtension for Labels (SKOS-XL) B.1. SKOS-XL Namespace and Vocabulary The Simple Knowledge Organization System is a data-sharing standard, bridging several different fields of knowledge, technology and practice. In the library and information sciences, a long and distinguished heritage is devoted to developing tools for organizing large collections of objects such as books or museum artifacts. These tools are known generally as "knowledge organization systems" (KOS) or sometimes as "controlled structured