From W3C Wiki
This is a description of a requirement for guidance and/or support for modelling thesauri with 'fundamental facets' (also called 'fundamental categories') using RDF.
Some thesauri organise their concept hierarchies at the highest level according to a set of 'fundamental facets', sometimes called 'fundamental categories'.
Take for example the AAT, which uses the following fundamental facets ...
Associated Concepts Facet Physical Attributes Facet Styles and Periods Facet Agents Facet Activities Facet Materials Facet Objects Facet
The design motivation is that each of these fundamental facets should be orthogonal ... i.e. no concept may be a member of more than one facet. However, this restiction may be broken in certain exceptional cases.
The SKOS-Core schema or the SKOS-Core documentation should provide clear support and guidance for how to model this type of structure, using RDF, RDFS, OWL and SKOS-Core.