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SKOS: Building taxonomies with minimum ontological commitment


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A short introduction to Simple Knowledge Organisation System (SKOS) - a W3C standard for representing taxonomies, thesuari, and other classification systems. Presented at the Semantic Web London meetup (April, 2017)

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SKOS: Building taxonomies with minimum ontological commitment

  1. 1. SKOS: Building taxonomies with minimum ontological commitment Szymon Klarman Grakn Labs Semantic Web London Meetup April 18, 2017
  2. 2. Simple Knowledge Organisation System • W3C standard (2009)… • …for sharing thesauri, taxonomies, classification schemes and subject heading systems… • …using the Semantic Web data model RDF.
  3. 3. Simple Knowledge Organisation System Car Motor vehicle Motorcycle "car" @en "automobile" @en "auto" @pl"samochod" @pl skos:broader Car washes Services skos:broaderskos:broader skos:relatedMatch Vehicles skos:inScheme Industry classification skos:inScheme skos:prefLabel skos:prefLabelskos:altLabel skos:altLabel
  4. 4. Knowledge organisation systems controlled vocabulary Expressiveness taxonomy thesaurus ontologyOntological commitment SKOS OWL/RDFS list of terms hierarchy hierarchy + relations classes instances properties
  5. 5. Ontological commitment & semantics motor vehicle a wheeled vehicle, powered by an internal combustion engine, that does not operate on rails car a motor vehicle, typically with 4 wheels, able to carry a small number of people
  6. 6. Ontological commitment & semantics
  7. 7. Ontological commitment & semantics ?x rdf:type ?y ?y rdfs:subClassOf ?z --------------------------- ?x rdf:type ?z Car Motor vehicle has engine some Combustion engine myTesla rdf:type rdfs:subClassOf rdfs:subClassOf Semantics = logical inference rdf:type rdf:type
  8. 8. Ontological commitment & semantics Car Motor vehicle myTeslaPhoto subject skos:broader X skos:broader Y = „Y has a broader meaning than X” semantics = shared understanding
  9. 9. Ontological commitment & semantics Domain: Real-world things Questions: -What are they? -What are they like? Semantics: Set-theoretic OWL/RDFS ontologies Domain: Information resources (and concepts). Question: What are they about? Semantics: No formal semantics. Integrity constraints imposed by the data model specs. SKOS taxonomies RDF data model
  10. 10. SKOS specification • concepts and labels • semantic relations • SKOS mappings • integrity constraints
  11. 11. Concepts and labels "car" @en "automobile" @en "auto" @pl"samochód" @pl skos:prefLabel skos:prefLabelskos:altLabel skos:altLabel skos:Concept rdf:type Car "A motor vehicle, typically with 4 wheels, able to carry a small number of people" @en skos:definition
  12. 12. Semantic relations Car Motor vehicle skos:broader Electric car skos:narrower skos:related Electric vehicle skos:broader skos:narrower
  13. 13. SKOS mappings Car Motor car skos:exactMatch Vehicles skos:inScheme Road traffic vocabulary Car (automatic) skos:inScheme skos:narrowMatch skos:inScheme skos:broadMatch
  14. 14. Integrity constraints (entailments) •skos:semanticRelation - domain & range = skos:Concept •skos:related - symmetric •skos:relatedMatch - symmetric •skos:broaderTransitive - transitive, inverseOf skos:narrowerTransitive •skos:broader - inverseOf skos:narrower •skos:broadMatch - inverseOf skos:narrowMatch •skos:narrowerTransitive - transitive, inverseOf skos:broaderTransitive •skos:narrower - inverseOf skos:broader •skos:narrowMatch - inverseOf skos:broadMatch •skos:closeMatch - symmetric •skos:exactMatch - symmetric, transitive
  15. 15. Integrity constraints (non-entailments) Car Motor vehicle skos:broader skos:broader Vehicle skos:broader Car Car wash skos:related skos:related Cleaning products skos:related
  16. 16. Integrity constraints (not consistent) "car" @en "automobile" @en skos:prefLabel Car skos:prefLabel "car" @en skos:prefLabel Car skos:altLabel
  17. 17. Integrity constraints (not consistent) Car Motor vehicle skos:broader skos:related Vehicle skos:broader Car Motor vehicle skos:broader skos:related
  18. 18. Integrity constraints (not consistent) Car Motor car skos:exactMatch skos:broadMatch Car Motor car skos:exactMatch skos:relatedMatch
  19. 19. SKOS + OWL/RDFS Car Motor vehicle powered by some Combustion engine myCar rdf:type rdfs:subClassOf rdfs:subClassOf myCarPhoto subject skos:broader skos:Concept rdf:type rdf:type owl:Class rdf:type rdf:type rdf:type
  20. 20. Curated SKOS taxonomies -AGROVOC Multilingual agricultural thesaurus agricultural-thesaurus - STW Thesaurus for Economics -UK Public sector vocabularies -EUROVOC European Union multilingual thesaurus
  21. 21. Crowdsourced SKOS taxonomies
  22. 22. Crowdsourced SKOS taxonomies •Films_about_technology •Films_about_artificial_intelligence •Films_about_nuclear_war_and_weapons •Robot_films •Android_(robot)_films •Terminator_films •Documentary_films_about_robotics •Films_about_computing •Films_about_security_and_surveillance •Films_about_telepresence
  23. 23. Crowdsourced SKOS taxonomies skos:Concept 1,561,776 skos:broader 3,262,643 skos:related 23,483 skos:exactMatch 307 dct:subject 24,941,650
  24. 24. Crowdsourced SKOS taxonomies crowdsourced taxonomy + crowdsourced tagging = very noisy data + highly imprecise categorisation But: less ontological committment  broader participation  knowledge acquisition bottleneck reduced  cost of building intelligent applications reduced
  25. 25. SKOS-based recommendations DBpedia movie recommender:
  26. 26. SKOS-based similarity Horror Movie Comedy skos:broaderskos:broader Monster movie Haunted house movie skos:broaderskos:broader Slapstick skos:broader A B C subject subject subject taxonomy taggedcontent
  27. 27. Boosting SKOS management Taxonomical knowledge Information resources SKOS taxonomy
  28. 28. Boosting SKOS management Taxonomical knowledge Information resources SKOS taxonomy Discovery •iterative •interactive •semi-automated Pool Party Semantic Suite (Semantic Web Company) DBpedia subjects reconciliation / import Concept extraction Recurrent term suggestion
  29. 29. Context disambiguation Movies „jaws" @en skos:altLabel „jaws" @en skos:altLabel Anatomy
  30. 30. Summary SKOS is an RDF-based standard for representing taxonomies, thesauri, etc. •Conceptually simple with minimum ontological commitment: •No complex formal semantics and logical implications •Laverages NL semantics and facilitates sharing it •Lower entry treshold for engaging experts/contributors/users •Structurally simple: •Easy to visualise and navigate •Easy to exploit with graph-based algorithms •Convenient bridge between structured and unstructured data.