VANN is a lightweight RDF vocabulary that provides properties for annotating descriptions of other vocabularies. Despite its small size, VANN plays a quietly essential role in the Linked Data ecosystem by standardizing how vocabulary authors declare namespace prefixes, document usage examples, and describe changes to their vocabularies. It is one of the most widely used meta-vocabularies in practice, appearing in the headers of countless OWL and RDFS vocabularies across the web.
Background
VANN was created by Ian Davis in 2005, during the early growth of the Semantic Web when new RDF vocabularies were proliferating rapidly. As vocabulary authors published their ontologies, there was no consistent way to indicate which namespace prefix should be used with a vocabulary, or to provide structured examples of how the vocabulary's terms should be applied. VANN addressed this gap with a deliberately minimalist approach, defining only the properties needed to annotate vocabulary documentation effectively.
The vocabulary was published at vocab.org, a site Davis maintained for hosting small, useful RDF vocabularies. Its simplicity and clear purpose led to rapid adoption, and VANN's properties became a de facto convention in vocabulary publishing.
Purpose & Scope
VANN's most commonly used properties are vann:preferredNamespacePrefix and vann:preferredNamespaceUri, which declare the short prefix and namespace URI that tools and applications should use when working with a vocabulary. These properties are consumed by vocabulary catalogs, prefix registries (such as prefix.cc), and RDF tooling to provide consistent namespace handling.
Additional properties include vann:usageNote for documenting how terms should be used, vann:example for linking to usage examples, and vann:changes for pointing to change documentation. Together, these properties provide a minimal but practical framework for vocabulary metadata.
Key Properties
| Property | Purpose |
|---|---|
vann:preferredNamespacePrefix |
The recommended short prefix for the vocabulary |
vann:preferredNamespaceUri |
The canonical namespace URI |
vann:usageNote |
A note about how to use the vocabulary |
vann:example |
A link to a usage example |
vann:changes |
A link to a description of changes since the last version |
Governance & Maintenance
VANN is maintained informally by its creator. It does not have a formal governance structure or standards body behind it. The vocabulary has been stable for many years, with no significant changes needed given its deliberately limited scope. Its namespace is managed through PURL persistent identifiers.
Notable Implementations
VANN properties appear in a vast number of published RDF vocabularies. The Linked Open Vocabularies (LOV) directory relies on vann:preferredNamespacePrefix and vann:preferredNamespaceUri to index and organize the hundreds of vocabularies it catalogs. Prefix registries like prefix.cc also reference these properties. Major vocabularies including DCAT, PROV-O, and many SPAR ontologies use VANN annotations in their published RDF files.
Related Standards
- VOAF -- The Vocabulary of a Friend, another meta-vocabulary that describes relationships between vocabularies