In knowledge organization systems, sometimes concepts are merged (for example, because the differences between concepts are not considered significant any longer). Normally, a "weaker" concept, say A, is bound to perish and gets some note attatched "Out of use, please use B".
How to put this on to the Linked Data Web?(*) Here our ideas: <A> a skos:Concept ; rdfs:label "Real Estate Loan"@en ; owl:deprecated "true"^^xsd:boolean ; dcterms:isReplacedBy <B> ; skos:historyNote "deprecated in version 8.06"@en ; skos:inScheme <C> . <B> a skos:Concept ; skos:prefLabel "Mortgage"@en ; skos:altLabel "Real Estate Loan"@en ; ... skos:inScheme <C> . <C> a skos:ConceptScheme ; ... owl:versionInfo "8.06" . The main goal was that people/applications who use the concepts of a KOS (e.g. with dcterms:subject) should be able to automatically discover deprecated concepts and to replace them by currently valid ones. The approach does not aim at an machine-readable record of historical states and state transitions of the KOS and its concepts. Some design decisions that could be questioned: 1) The former prefLabel of <A> has been moved to <B> as an altLabel. As far as I can see, the spec doesn't prohibit using it also as a prefLabel for <A>, but it feels more appropriate to avoid this by using a plain rdfs:label. (As a nice side effect, concept <A> doesn't show up when the KOS is queried for prefLabel/altLabel/hiddenLabel) 2) All skos:semanticRelations (broader, narrower, related etc.), and also all skos:altLabel/hiddenLabels, were removed from the deprecated concept A and, where appropriate, attached to concept B. 3) A deprecated skos:Concept still is a skos:Concept (may be in use as such; especially, may have still mappings from other vocabularies, outside the scope of the actual KOS) 4) Versioning is done in a very informal way by attaching owl:versionInfo to the skos:ConceptScheme. The skos:Concepts are deliberately not versioned, because this would put a heavy burden on their use. Also, the skos:ConceptScheme <C> currently does not have a "versioned" URI (which could be done, but I'm not sure if it would be worth the increased complexity). The history is only represented informally in a skos:historyNote. 5) Prior versions of the skos:ConcpetScheme are on the web for reference, however, the URIs for concepts and the scheme itself resolve to the current version. (We will try to prohibit indexing of prior versions by semantic search engines in order to avoid the aggregation of not longer valid attributes and relations for a concept) I wonder what you think about this approach. Cheers, Joachim * Some work to build on has been collected at http://www.w3.org/2001/sw/wiki/SKOS/Issues/ConceptEvolution