Module 2

Introduction to Vocabularies

SKOS — the W3C standard for publishing controlled vocabularies as linked data.

What is a Vocabulary?

A vocabulary (controlled vocabulary, thesaurus, or taxonomy) provides a standardised set of terms with unique identifiers — so that two systems referring to "High Risk" mean exactly the same thing.

Human understanding — labels and definitions in plain language
Machine processing — unique IRIs that computers can match unambiguously

Types of Vocabularies

Glossary — concepts with labels and definitions only
Taxonomy — adds broader/narrower hierarchy
Thesaurus — taxonomy + non-hierarchical associations + synonym control

SKOS Core Properties

skos:ConceptSchemeThe container for your vocabulary — holds metadata like title, creator, and links to all concepts.

skos:ConceptA single term in your vocabulary. Must have an IRI, a prefLabel, and a definition.

skos:prefLabelThe preferred human-readable label. Only one per language tag. Required by VocPub.

skos:altLabelAlternative labels — synonyms, acronyms, or superseded terms. Multiple allowed.

skos:definitionA complete textual definition. Required by VocPub. Should be self-contained.

skos:broaderPoints to a more general concept. Enables hierarchy navigation.

skos:narrowerPoints to a more specific concept. Often inferred rather than stated explicitly.

skos:relatedA non-hierarchical association between two concepts in the same scheme.

skos:topConceptOfDeclares this concept is at the top of its hierarchy. Links back to the ConceptScheme.

skos:scopeNoteClarifies what is included or excluded from a concept's scope.

Annotated Turtle

Hover over each coloured token to see what it does.

Exercise — Hover the tokens to learn each part

Hover over each coloured token to see what it does.

bushfire-risks.ttl

@prefix risk: <https://example.org/risk/> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix dcterms: <http://purl.org/dc/terms/> .

risk:BushfireRiskLevels
    a skos:ConceptScheme ;
    dcterms:title   "Australian Bushfire Risk Levels"@en ;
    skos:hasTopConcept  risk:Extreme, risk:High, risk:Medium, risk:Low .

risk:High
    a skos:Concept ;
    skos:prefLabel   "High Risk"@en ;
    skos:definition "Conditions likely to result in significant, fast-moving fire."@en ;
    skos:altLabel   "High"@en ;
    skos:topConceptOf  risk:BushfireRiskLevels .

Hover a coloured term above to see its explanation.

Hierarchy: broader and narrower

SKOS hierarchies follow the all-some rule: if Grassfire is narrower than Bushfire, then all grassfires are bushfires, but only some bushfires are grassfires.

Exercise — Browse the concept hierarchy

Click any concept to see its SKOS properties.

VocPub Profile

The VocPub profile (used in Australian Government linked data systems) requires every concept to have skos:prefLabel, skos:definition, and membership in a skos:ConceptScheme.

Module 1