W3C SKOS
SKOS is a W3C model for concept schemes, expressed in RDF, that gives a controlled vocabulary labels and relations without turning it into an ontology.
What it is
SKOS — Simple Knowledge Organization System — is a W3C Recommendation for representing concept schemes such as thesauri, taxonomies and subject heading lists in RDF. Concepts carry skos:prefLabel, skos:altLabel and skos:hiddenLabel, and relate through skos:broader, skos:narrower and skos:related; mapping properties such as skos:exactMatch connect concepts across schemes.
What it gives the knowledge layer
It gives an organisation's vocabulary a machine-readable home: terms become identified concepts with labels, synonyms and a place in a hierarchy, so an agent can expand a query without a bespoke lookup table. Mapping properties let two taxonomies be connected rather than merged.
Where the spec lives
The normative document is the SKOS Reference, a W3C Recommendation defining the classes, properties and semantics. W3C also maintains a SKOS wiki page with background and implementation pointers — the accessible counterpart to the ISO work at ISO 25964.
What it does not solve
SKOS describes concepts and their relations, not the facts about the things those concepts name: a product category carries labels and a place in a hierarchy, not a price. It is deliberately not an ontology language, so it carries none of the class axioms or entailment that OWL does — that is ontology work.
FAQ
No. SKOS describes concepts and the relations between them: labels, broader, narrower and related links, and mappings to other schemes. It does not describe the things those concepts name.
A hidden label is a lexical form a search or indexing system should match but that is not appropriate to display, such as a misspelling or an internal shorthand.
They let two vocabularies be related without merging them: each scheme keeps its own labels and owners, and an agent can traverse from a term it holds to a term another system uses.
No. It gives structure and labels, not validation of facts. A scheme can be internally tidy and still describe a domain wrongly, and the relations carry no reasoning.
Sources
- SKOS Simple Knowledge Organization System Reference — W3C Recommendation; the normative definition of SKOS classes, label properties, semantic relations and mapping properties.
- SKOS — W3C Semantic Web wiki — background, scope and implementation pointers for the model.