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SKOS and Linked Data


Presentation at ISKO-UK Linked Data: The Future of Knowledge Organization on the Web conference. More at http://www.iskouk.org/events/linked_data_sep2010.htm

Presentation at ISKO-UK Linked Data: The Future of Knowledge Organization on the Web conference. More at http://www.iskouk.org/events/linked_data_sep2010.htm

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  • electronic service delivery
  • 32 constructs in total


  • 1. SKOS and Linked Data Antoine Isaac ISKO, London, Sept. 14 th 2010
  • 2. Personal background
    • Europeana
    • Web & Media Lab , Vrije Universiteit Amsterdam
    • W3C Library Linked Data group
    • (2006-2009) W3C Semantic Web Deployment group
      • SKOS
  • 3. Towards a web of culture data
  • 4. Government data again? http://standards.esd.org.uk/
  • 5. Government data again?
  • 6. SKOS
    • Simple Knowledge Organization System
    • Scope: knowledge organization systems (KOS) such as thesauri, classification systems, subject heading lists…
    • SKOS is for representings KOSs in RDF in a simple way
  • 7. Representing semantics
    • The formal way: OWL Semantic Web ontology language
    • Used for ontologies that enable machine reasoning
    • Mother is a class
    • It is the intersection of the classes Woman and Parent
    • Parent is the class of entities of type Person that are related to at least one other resource of type Person using the child property
  • 8. SKOS is not for formal ontologies
    • Turning KOSs into ontologies is possible, but KOSs
      • are large
      • have softer “semantics”
        • Parent RelatedTerm Child
      • have often a focus on terminological information
        • Child UsedFor Offspring
    • Softer semantics can be useful as such for many applications!
      • Semantic search, annotation…
  • 9. Basic SKOS
    • A set of features common to various KOS types and useful for many applications
    • Concepts
    • Lexical properties
    • Semantic relations
    • Notes
  • 10. Thesaurus example Animals cats UF ( used for ) domestic cats RT ( related term ) wildcats BT ( broader term ) animals SN ( scope note ) used only for domestic cats domestic cats USE cats wildcats
  • 11. Concepts and labels cats UF ( used for ) domestic cats skos: = http://www.w3.org/2004/02/skos/core# rdf: = http://www.w3.org/1999/02/22-rdf-syntax-ns# ex: = http://example.org/
  • 12. Note: multilingual labels
  • 13. Semantic relations cats RT ( related term ) wildcats BT ( broader term ) animals
  • 14. A SKOS graph animals cats UF domestic cats RT wildcats BT animals SN used only for domestic cats domestic cats USE cats wildcats
  • 15. SKOS mappings
    • SKOS allows bridging across KOSs from different contexts
    KOS 1: animals cats wildcats KOS 2: animal human object
  • 16. Other features
    • Concept grouping
      • skos:Collection, skos:member…
    • Concept documentation
      • skos:example…
    • SKOS-XL: extension for more complex representation of labels
    • Note: SKOS can be extended as any other RDF vocabulary
  • 17. Semantics for SKOS
    • There are some basic constraints on SKOS data
    • E.g., a concept has only one prefLabel per language
  • 18. Semantics for SKOS
    • There are rules to infer new facts
    • E.g., broader and narrower are inverse of each other
  • 19. Semantics for SKOS
    • Minimal semantic commitment:
    • SKOS must cope with existing information and not infer new data beyond what KOS publishers intend
  • 20. References
    • SKOS Reference http://www.w3.org/TR/skos-reference
    • SKOS Primer http://www.w3.org/TR/skos-primer
    • SKOS homepage http://www.w3.org/2004/02/skos
    • SKOS wiki http://www.w3.org/2001/sw/wiki/SKOS
    • SKOS mailing list [email_address]
  • 21. Benefits of SKOS?
    • Easily fitting KOSs into the Semantic Web & Linked Data vision
    • Web-oriented representation
    • Re-use & sharing of concepts and their descriptions
    • Linking between concepts from different contexts
  • 22. Demo
    • Subject heading lists as SKOS linked data
    • American LCSH http://id.loc.gov
    • French RAMEAU: http://stitch.cs.vu.nl/rameau
    • German SWD: http://d-nb.info/gnd/
    • mapped using manual links from the MACS project http://macs.cenl.org
    • Starting from http://id.loc.gov/authorities/sh85014310#concept
  • 23.  
  • 24.  
  • 25.  
  • 26.  
  • 27.  
  • 28. Linked Data?
    • 1. Use URIs as names for things
    • 2. Use HTTP URIs so that people can look up those names
    • 3. When someone looks up a URI, provide useful information using standards (RDF, SPARQL)
    • 4. Include links to other URIs, so that they can discover more things
    • Tim Berners-Lee, http://linkeddata.org/
  • 29.  
  • 30.  
  • 31. SKOS Implementations Miles, Bechhofer, SKOS Implementation Report , May 19th 2009 http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/implementation.html
  • 32. Some landmark SKOS implementations
    • Swedish National Library’s Libris catalogue and thesaurus http://libris.kb.se/
    • Library of Congress’ vocabularies, including LCSH http://id.loc.gov/
    • DNB’s Gemeinsame Normdatei (incl. SWD subject headings) http://d-nb.info/gnd/
    • BnF’s RAMEAU subject headings http://stitch.cs.vu.nl/
    • OCLC’s DDC classification http://dewey.info/ and VIAF http://viaf.org/
    • STW economy thesaurus http://zbw.eu/stw
    • National Library of Hungary’s catalogue and thesauri http://oszkdk.oszk.hu/resource/DRJ/404 (example)
    • Wikipedia categories through Dbpedia http://dbpedia.org/
    • New York Times subject headings http://data.nytimes.com/
    • IVOA astronomy vocabularies http://www.ivoa.net/Documents/latest/Vocabularies.html
    • GEMET environmental thesaurus http://eionet.europa.eu/gemet
    • Agrovoc http://aims.fao.org/
    • Linked Life Data http://linkedlifedata.com/
    • Taxonconcept http://www.taxonconcept.org/
    • UK Public sector vocabularies http://standards.esd.org.uk/ (e.g., http://id.esd.org.uk/lifeEvent/7 )
  • 33. KOS Alignments?
    • Quite many of them are linked to some other resource
    • LCSH, SWD and RAMEAU interlinked through MACS mappings
    • GND -> DBpedia, VIAF
    • Libris -> LCSH
    • Agrovoc -> CAT, NAL, SWD, GEMET
    • NYT -> freebase, DBpedia, Geonames
    • dbPedia links are overwhelming
      • Hungary, STW, TaxonConcept, GND…
  • 34. Issues: semantic alignment of SKOS data
    • In a linked data environment, the most interesting applications are the ones that cross contexts
    • Mapping data between concept schemes is still scarce
    • More efforts are needed
      • Automatic or manual or a mixture of both
  • 35. Issues: linking KOS data to other resources
    • KOSs become valuable when they bring a “semantic layer” over other resources
      • E.g. books and the topics they are about
    • Existing links are often only implicit in the data—using labels of concepts not their identifiers
    • Semantic annotation with KOS should be a main target
      • Cf. Drupal’s taxonomy plug-in
  • 36. Conclusion
    • Publication and linking of linked KOS data is still work in progress, but
    • We are now in position of realizing the issues and working towards solving them
    • We can start building applications that make use of the wealth of data already available or yet to come
      • Many KO resources to re-use and link to
  • 37. Thank you! [email_address]
  • 38. Acknowledgements
    • Participants of the Semantic Web Deployment working group
      • Alistair Miles, Sean Bechhofer, Ed Summers, Tom Baker, Guus Schreiber…
    • Library of Congress
    • French National Library
    • German National Library
    • MACS team (Swiss National Library)
    • EuropeanaConnect project