AGROVOC Thesaurus Concept Scheme
AGROVOC was first developed in the early 80s, as a thesaurus to support uniform indexing of the AGRIS bibliographic database, and then of the whole FAO bibliographic catalogue. At the beginning, AGROVOC was developed in handful of languages, but the number of supported languages grew over the years to over 20 today.
Also the way to store and publish AGROVOC has evolved over the years. AGROVOC is now primarily an RDF/SKOS-XL resource, a concept scheme.
While terms are central to a thesaurus, concepts are the central notion of a concept scheme. A SKOS concept scheme is then formed by:
- are meant to represent the “meaning” of terms. One could take a concept as the set of all terms considered to be translation of one another in various languages.
- AGROVOC concepts are expressed as skos:Concept
- Concepts are given dereferenceable URIs (= URL), such as http://aims.fao.org/aos/agrovoc/c_12332 for maize.
- or labels, are the actual terms used to name things or abstract concepts
- For example maize, maïs, 玉米, ข้าวโพด, are all labels for the same concept in English, French, Hindi respectively.
AGROVOC labels are expressed by means of the SKOS extension for labels, SKOS-XL. The predicates used are:
- skosxl:prefLabel, used for preferred terms (“descriptors” in thesaurus terminology), and
- skosxl:altLabel, used for non preferred terms.
- relations, which may be between concepts or terms
- Hierarchical relations between concepts correspond to the classical thesaurus relations broader/narrower (BT/NT). AGROVOC uses the SKOS predicates skos:broader, skos:narrower to express them.
- For non-hierarchical relations between concepts and terms, AGROVOC uses properties that are currently under revision.
- Note that in the case of terms this is possible because of the use of SKOS-XL.
The figure below represents a fragment of AGROVOC concept scheme. In that figure, circles are used to represent objects with URIs, boxes are used for literal values, and AV, skos and skosxl are short for http://www.aims.fao.org/agrovoc/ “http://www.w3c.org/2008/05/skos-xl#” http://www.w3c.org/2004/02/skos/core#” respectively.
The figure shows two concepts linked by a (hierarchical) skos:broader relation, and an example of SKOS-XL labels for each concept.
All domain-specific properties used in AGROVOC to enriching the description of AGROVOC concepts in RDF are collected in a vocabulary called agrontology. Agrontology is undergoing a deep analysis in order to make very explicit the modelling style adopted in its various topic areas.