Concepts are ‘units of thought’ that exist in a domain. Concepts are represented by terms. In SKOS concepts are formalised as skos:concept, identified by dereferenceable URIs (URLs). In Skosmos, URIs are shown on each concept page.
Terms are the actual names used to refer to a concept. For example POLITICAL PROTEST, POLIITTINEN VASTARINTA, and POLITIČNI PROTEST are all labels for the same concept in English, Finnish and Slovenian, respectively.
Labels are expressed by means of SKOS predicates:
- skos:prefLabel is used for ‘Preferred Terms’ in classical thesaurus terminology
- skos:altLabel is used for ‘Non-Preferred’ or ‘Use For’ terms in classical thesaurus terminology.
- Hierarchical relations between concepts are expressed in SKOS by the predicates skos:broader and skos:narrower, which correspond to the classical thesaurus relations Broader/NarrowerTerm (BT/NT).
- Non-hierarchical relations express a notion of ‘relatedness’ between concepts and are represented in SKOS via the skos:related predicate, which corresponds to the classical thesaurus relation Related Term (RT).
- Definitions are expressed as ‘skos:definition’
- Scope Notes are expressed as ‘skos:scopeNote’
- History Notes are expressed as ‘skos:historyNote’
- Definition Sources are expressed as ‘xkos:additionalContentNote’
The table below shows the correspondence between SKOS/XKOS names, those used in Skosmos (see Using ELSST).