The Unified Astronomy Thesaurus (UAT) provides a comprehensive,
interlinked set of concepts relevant for astronomy and astrophysics using
SKOS. It is taken up in the Virtual Observatory at least for registry
subject keywords. For various reasons, it is desirable to have the UAT
available subject to the constraints laid down in the IVOA Vocabularies
in the VO 2 specification. This Note describes the rationale and the
details of the UAT adoption by the IVOA.
In this document, we discuss practices related to the use of RDF-based
consensus vocabularies in the Virtual Observatory, that is the creation,
publication, maintenance, and consumption of hierarchical word lists
agreed upon within the IVOA. To cover the wide range of use cases
envisoned, we define different vocabulary types for informal knowledge
organisation on the one hand, and strict hierarchies of classes and
properties on the other. While the framework rests on the solid
foundations of W3C RDF, provisions are made to facilitate using IVOA
vocabularies without specific RDF tooling. Non-normative appendices
detail the current vocabulary-related tooling.
