Update on SKOS and Use Cases Ecoterm, 5 October 2009 Antoine Isaac Vrije Universiteit Amsterdam W3C Semantic Web Deployment working group http://www.few.vu.nl/~aisaac
Preamble: acknowledgements Participants of the W3C Semantic Web Deployment Working Group Tom Baker, Guus Schreiber, Alistair Miles, Sean Bechhofer, Ralph Swick, Ed Summers, Jon Phipps, Margherita Sini, Diego Berrueta, Clay Redding, and many others… http://www.w3.org/2006/07/SWD/
SWD working group goals Various aspects of deploying Semantic Web technology: • Publication guidelines • URI management • Embedding RDF in (X)HTML pages • RDFa • RDF representation of existing vocabularies • SKOS
SKOS • Simple Knowledge Organization System • SKOS is a model to represent KOSs on in RDF in a simple way • Not directly addressing complex terminological issues SKOS is now an official W3C recommendation!
W3C standardization process • Input: draft specification (SKOS 2005) • Collect use cases & derive requirements • Create issues list: requirements that cannot be handled by the draft spec • Propose resolutions for issues • Get consensus on new spec • Find two independent implementations for each feature in the spec • Continuously: asked for public feedback/comments • Lot of feedback coming from firstname.lastname@example.org • Guus Schreiber
What then? • Update on SKOS
Basic SKOS • Concepts • Lexical properties • Semantic relations • Notes Things that have remained quite stable since SKOS 2005
Example: SKOS graph animals NT cats cats UF domestic cats RT wildcats BT animals SN used only for domestic cats domestic cats USE cats wildcats
Some other stable features • Collections of concepts • skos:Collection, skos:OrderedCollection, skos:member • Explicit representation of Concept Schemes • skos:ConceptScheme, skos:inScheme, skos:hasTopConcept
New stuff • Mapping relations • SKOS-XL extension • Discussion on semantics • (Notations)
Mapping • A crucial set of use cases, where semantic links across KOSs have to be exploited • Integrated navigation and search • Real-world cases: • Johan Stapel, Nat. Library of the Netherlands
Networking controlled vocabularies in SKOS KOS 1: animals cats wildcats KOS 2: animal human object • closeMatch and exactMatch for equivalence • exactMatch is stronger and context-independent (transitive) • broadMatch and narrowMatch for hierarchical links • relatedMatch for other cases of interest Some were here in 2005, but as a non-stable extension
Relationships between lexical labels From SKOS Use Cases: • Use Case #3 — Semantic search service across mapped multilingual thesauri in the agriculture domain “The AIMS project includes String-to-String relationships” “Requires: R-RelationshipsBetweenLabels” • In basic SKOS, labels are RDF literals and cannot be subjects of RDF statements
Relationships between lexical labels skos-xl:labelRelation ex:translation • Done as an extension: SKOS-XL • skos-xl:Label • skos-xl:labelRelation
Semantics for SKOS? • The SKOS model gives formal constraints on SKOS data • But SKOS must cope with existing information, and not infer new knowledge, beyond what KOS designers intend • Minimal semantic commitment • Over-commitment harms interoperability
Example: semantics of labels • SKOS assumes some characteristics for the different kinds of labels • A concept has only one prefLabel per language
Example: semantics of broader • Is skos:broader "transitive"? • It can be wrong, sometimes! • Some KOSs are not always hierarchically clean • skos:broaderis not transitive in general
Semantics of broader skos:broaderhas a super-property skos:broaderTransitive with semantics of “has ancestors” • 1: every broader implies a broaderTransitive • 2: broaderTransitive is transitive!
What are the benefits? • Semantic Web features applied to KOSs: • Web-oriented modeling • Re-use & sharing of resources (concepts!) and descriptions of resources • Linking between resources from different contexts • Extensibility
What then? • SKOS implementations
Current SKOS Implementations • Report by SWD group • Implementations: tools to exploit or create SKOS data • Vocabularies: KOSs converted to SKOS • 27 contributions • Give an idea on (early) usage of SKOS constructs • and on applications: mostly vocabulary services
A blossoming field The report is a partial snapshot, it misses a lot: • KOSs: • NASA vocabularies • GEMET? • Agrovoc? • Search applications: • Libris: http://libris.kb.se/ • Europeana Thought Lab: http://www.europeana.eu/portal/thought-lab.html • Annotation tools
Next steps? • By the community, for the community • Gathering exemplar conversions and publications • Extensions or good practices to deal with more specific problems, like coordination • SKOS application profiles? • Take-home message: get (or remain) involved!
Thanks! • Some links • SKOS homepage: www.w3.org/2004/02/skos/ Soon equipped with a community-oriented wiki! • SKOS Reference: www.w3.org/TR/skos-reference/ • SKOS Primer: www.w3.org/TR/skos-primer/ • A demo I could make: • LCSH as SKOS linked data : http://id.loc.gov • mapped to French RAMEAU: http://stitch.cs.vu.nl/rameau