Type	Ontology
Coverage	Limited / around 1750 Units originating from 10 systems of units for 880 quantity kinds
Hosted by	public charity non-profit organization
Homepage	https://QUDT.org https://github.com/qudt/qudt-public-repo

The QUDT ontology includes

• physical constants, quantity kinds, units, unit systems, prefixes and dimension vectors
• a semantic description of the named entries including the relation to other entries
• translations to other standards of unit description

QUDT is modelled in OWL (Web Ontology Language). Other descriptions and interfaces are available like RDF/XML, TURTLE, JSON or SPARQL.

QUDT not only focuses on defining models and a publicly available vocabulary to express quantities and units but also wants to offer a translation between existing standards doing the same. Therefore, the ontology also names UCUM, UNECE, IEC 61360 and LaTeX codes for the entries.

QUDT originated from a NASA project trying to define a semantic specification for units of measure, quantity kind and dimensions used in science and engineering. Today it is governed by a board of directors from different research institutes and the industry.