RECENT CHANGES TO SKOS Overview -------- The latest verson of the the SKOS vocabulary (SKOS2008) is defined in a new namespace http://www.w3.org/2008/05/skos#. The previous one (SKOS2004) is still available and valid http://www.w3.org/2004/02/skos/core#; however users of SKOS are encouraged to migrate towards SKOS2008. Typically you might hear SKOS2008 referred to as SKOS instead of SKOS Core. The majority of the changes in SKOS2008 involve the increased use of OWL for modeling. SKOS2008 vocabulary elements are now defined to be of type owl:Class, owl:DatatypeProperty, owl:ObjectProperty instead of rdfs:Class and rdf:Property, as they were in SKOS2004. Using OWL allows for more expressivity about the components of the SKOS vocabulary. (what's the best way to explain this?) The SKOS2008 vocabulary is much more compact: 347 triples as compared with 844 for SKOS2004. Interestingly SKOS2008 also uses features from the skos vocabulary itself such as skos:changeNote and skos:definition. The SKOS Reference is currently in Last Call, and the SWD WG are actively seeking feedback on the public-swd-wg@w3.org discussion list. Below is more detailed information about the changes. It's very important to the w3c recommendation process that the working group get all kinds of feedback. Concepts and Concept Schemes ---------------------------- The SKOS resources skos:Concept, skos:ConceptScheme, skos:Collection, skos:OrderedCollection are now of type owl:Class instead of rdfs:Class. This allows skos:Concept to be defined as disjoint with skos:ConceptScheme, which is a useful way of constraining concepts so that they cannot also be concept schemes. In addition skos:inScheme is now of type owl:ObjectProperty instead of rdf:Property. Both skos:TopConcept and skos:CollectableProperty were dropped. However skos:hasTopConcept was introduced to indicate that a concept scheme has a particular concept as a top level concept. Labels ------ The lexical labeling properties skos:prefLabel, skos:altLabel, skos:hiddenLabel are now of type owl:DatatypeProperty. They are also likely to be subclasses of rdfs:Label as they were in SKOS2004. Documentation Properties ------------------------ The skos:note, skos:changeNote, skos:definition, skos:example, skos:historyNote, skos:scopeNote, skos:editorialNote were changed from being of type rdf:Property to owl:ObjectProperty. skos:privateNote and skos:publicNote which were marked as deprecated in SKOS2004 have been removed. Since they are object properties these note relationships can point at resources which have additional metadata associated with them. In addition skos:symbol, skos:prefSymbol and skos:symbol have been dropped because there were no use cases or requirements for it, so they were deemed out of scope. Semantic Relations ------------------ The semantic relation properties skos:broader, skos:narrower and skos:related have been updated to be of type owl:ObjectProperty. The skos:broader and skos:narrower properties are no longer transitive, and instead extend two new properties skos:broaderTransitive and skos:narrowerTransitive, both of which are also transitive. The reason for this is to allow these relations to be used in vocabularies that are less rigorous that standard thesauri, while still allowing the narrowerTransitive and broaderTransitive properties to be inferred applications that want them. In addition skos:related is no longer a sub-property of rdfs:seeAlso. Some deprecated relations such as skos:broaderGeneric, skos:broaderInstantive, skos:broaderPartitive, skos:related, skos:relatedHasPart, skos:relatedPartOf have been removed from the new namespace. Mapping Relations ----------------- SKOS2008 includes some new vocabulary elements for mapping concepts from one concept scheme to another: skos:exactMatch, skos:broadMatch, skos:narrowMatch, skos:relatedMatch. All of them are sub-properties of skos:mappingRelation, which has skos:Concept as both its domain and range. Subjects -------- SKOS2004 had vocabulary elements like skos:subject, skos:isSubjectOf, skos:isPrimarySubjectOf and skos:subjectIndicator, but they have been removed in the latest version of SKOS since they were deemed out of scope. Also, there are other vocabularies like DublinCore where relations of this kind are in scope. Notations --------- A new owl:DatatypeProperty skos:notation was introduced to allow concepts to be associated with notations such as classification codes. Notations are different from labels in that they tend not to be recognizable as a sequence of words in any natural languge. SKOS eXtension for Labels (skos+xl) ----------------------------------- XL is a separate vocabulary with its own URI namespace http://www.w3.org/2008/05/skos-xl#. The idea behind XL is to allow lexical labels to be resources, which in turn allows them to be related together. XL includes the skosxl:prefLabel skosxl:altLabel, skosxl:hiddenLabel which mirror the lexical labeling properties in SKOS proper, but are of type owl:ObjectProperty instead of owl:DatatypeProperty. In addition skosxl:labelRelation allows labels to be related together. The intent is for users to extend skos:labelRelation to build up vocabularies of relations between labels, like acronymy etc.