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DDC, SKOS, and Linked Data on the Web

DDC, SKOS, and Linked Data on the Web. Michael Panzer Global Product Manager, Taxonomy Services OCLC. Overview. Why transform the DDC into a SKOS vocabulary? Creating URIs What is a concept? What is an information resource? Analyzing DDC for modeling in RDF/SKOS Identifying concepts

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DDC, SKOS, and Linked Data on the Web

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  1. DDC, SKOS, and Linked Data on the Web Michael Panzer Global Product Manager, Taxonomy Services OCLC

  2. Overview • Why transform the DDC into a SKOS vocabulary? • Creating URIs • What is a concept? • What is an information resource? • Analyzing DDC for modeling in RDF/SKOS • Identifying concepts • Aligning DDC elements with SKOS classes and properties • Modeling sematic relationships • Integration into RESTful web services (if we have time)

  3. Why transform the DDC into a SKOS vocabulary? • Participation in “data web” is crucial for knowledge discovery tools • SKOS as publication format • Enabling data interoperability • Extensible, but “dumbing down” possible • Hospitability for terminologies; agile publication possible as soon as recommendation status is reached • Broadening the base of Dewey use cases and users • Rethinking access to KOS in general • Caution: Most research problems of semantic integration or vocabulary construction neither solved nor touched by SKOS!

  4. [Checklist: Webification of KOS] • (Infra-)Structural choke points • Design of identifiers • Design of verbal designators (“verbal plane”) • Data representation • Vocabulary enhancement • User contribution • Versioning • Vocabulary registries

  5. Cool URIs for the DDC (lightning overview) • Approaches to URI design • Encoding resource metadata into URIs? • Axiom of URI opacity • Genericity of resources • Dimensions of variance: time, language, format • Framing of concept instantiation • Role of Dewey classes for URIs • Classes as center of identification for DDC concepts • Information resources vs. non-information resources in web architecture

  6. Example URIs • Generic URI • http://dewey.info/class/338.4 • Specific time • http://dewey.info/class/338.4/2007/05/25 • http://dewey.info/class/338.4/e22 • Specific time & language • http://dewey.info/class/338.4/2007/05/25/about.en • Specific time, language & format • http://dewey.info/class/338.4/2007/05/25/about.en.skos

  7. Example URIs • Concept vs. representation URIs • http://dewey.info/class/338.4/ • http://dewey.info/class/338.4/about • Caveat: template still might change syntactically, e.g. • http://dewey.info/class,2007-05/338.4?$lang=en&$format=skos • Is the identifier strategy sound? • Application to SKOS

  8. Analyzing DDC for modeling in RDF/SKOS • What to include? What makes sense as Linked Data? • DDC is fairly complex: • Manual, external and internal tables, schedules, Relative Index, … • Regular, optional numbers; number spans, centered entries, … • Elaborate note structure • Singled out as skos:Concepts right now: • Listed schedule numbers (including built numbers) • Number spans • Centered entries • Relative Index terms (in different namespace)

  9. Analyzing DDC for modeling in RDF/SKOS skos:relatedMatch • 370.11 Education for specific objectives • 370.113 Vocational education • 370.113085 Parents--vocational education • 370.1130941 Vocational education--Great Britain • 370.1130973 Vocational education--United States skos:relatedMatch Mapped LCSH Relative Index Career education Career education--United States Career education--United States--Curricula Core competencies … Vocational education Vocational training centers Career development Career education Education of employees Employee development Human resource development …

  10. 370.113Vocational education Class here career education, occupational training, vocational schools Class on-the-job training, vocational training provided by industry in 331.2592 For vocational education at secondary level, see 373.246; for adult vocational education, see 374.013 See also 331.702 for choice of vocation; also 371.425 for vocational guidance in schools skos:notation skos:prefLabel skos:related Analyzing DDC for modeling in RDF/SKOS

  11. RDF model: Class (1) • <class/370.113/2007/12> a skos:Concept ; • skos:inScheme <scheme/2007/12> ; • dct:created "1996-06-01T00:00:00.0-05:00"^^<http://purl.org/dc/terms/W3CDTF> ; • dct:updated "2003-03-26T00:00:00.0-05:00"^^<http://purl.org/dc/terms/W3CDTF> ; • skos:notation "370.113"^^<ddc:Notation> ; • skos:prefLabel "Vocational education"@en ; • skos:broader <class/370.11/2007/12> ; • skos:narrower <class/370.113085/2007/12> , • <class/370.1130941/2007/12> , • <class/370.1130973/2007/12> ; • skos:related <class/331.2592/2007/12> , • <class/373.246/2007/12> , • <class/374.013/2007/12> .

  12. RDF model: Class (2) • <class/370.113/2007/12> skos:relatedMatch • <http://tspilot.oclc.org/lcsh/sh%2085020255%20> , • <http://tspilot.oclc.org/lcsh/sh%2000002431%20> , • <http://tspilot.oclc.org/lcsh/sh%2085144178%20> , • <http://tspilot.oclc.org/lcsh/sh%2096002453%20> .

  13. RDF model: Class (3) • <class/370.113/2007/12> ddc:hasIndexTerm <index/Career%20development> , • <index/Career%20education> , • <index/Education%20of%20employees> , • <index/Employee%20development> , • <index/Human%20resource%20development> , • <index/Job%20training> , • <index/Occupational%20training> , • <index/Retraining%E2%80%94vocational%20education> , • <index/Staff%20development> , • <index/Training%E2%80%94employee%20education> , • <index/Vocational%20education> , • <index/Vocational%20schools> , • <index/Vocational%20training> , • <index/Work%20training> .

  14. RDF model: Class (0) • @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . • @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . • @prefix skos: <http://www.w3.org/2008/05/skos#> . • @prefix ddc: <http://dewey.info/schema-terms/> . • @prefix owl: <http://www.w3.org/2002/07/owl#> . • @prefix dct: <http://purl.org/dc/terms/> . • @base <http://dewey.info/> . • ddc:hasIndexTerm rdfs:subPropertyOf skos:relatedMatch . • ddc:isIndexTermOf rdfs:subPropertyOf skos:relatedMatch ; • owl:inverseOf ddc:hasIndexTerm . Extending SKOS

  15. RDF model: Relative Index Terms • <Concept rdf:about="index/Job%20training"> • <inScheme rdf:resource="index/2007/12"/> • <prefLabel xml:lang="en">Job training</prefLabel> • <ddc:isIndexTermOf rdf:resource="class/370.113/2007/12"/> • </Concept> • <Concept rdf:about="index/Job%20training"> • <related rdf:resource="index/Vocational%20education"/> • </Concept>

  16. RDF model: Gathering assertions about a resource

  17. Modeling concept history events • Tracking and exposing change processes for discovery • Two recent positions: • Tennis: Augmenting SKOS with generic skos:ConceptInstance to indicate version- and vocabulary-specific skos:Concepts • Voss: Pragmatic approach focusing on retrieval; linking versions with skos:mappingRelation

  18. Modeling concept history events • Some problems • Change on concept level • Labels, relations, etc. • Change on scheme (inter-concept) level • Exhaustive change of concepts • Complex relocation/discontinuation, splitting of concept (1-to-many) • Simple relocation/discontinuation (1-to-1) • Partial change of concepts • Melding of a concept (integrating new topics, many-to-1) • Extensive revisions (many-to-many)

  19. Simple relocation/discontinuation • <Concept rdf:about="class/370.19/2007/12"> • <inScheme rdf:resource="scheme/2007/12"/> • <dct:created rdf:datatype="http://purl.org/dc/terms/W3CDTF">1996-06-01T00:00:00.0-05:00</dct:created> • <dct:updated rdf:datatype="http://purl.org/dc/terms/W3CDTF">2001-03-13T00:00:00.0-05:00</dct:updated> • <notation rdf:datatype="ddc:Notation">370[.19]</notation> • <prefLabel xml:lang="en">Psychological principles</prefLabel> • <broader rdf:resource="class/370.1/2007/12"/> • <historyNote rdf:parseType="Resource"> • <dct:isReplacedBy rdf:resource="class/370.15/2007/12"/> • </historyNote> • <historyNote rdf:parseType="Resource"> • <dct:isReplacedBy rdf:resource="class/306.43/1996"/> • </historyNote> • </Concept>

  20. Simple relocation/discontinuation • Two different representations of concept history modeled by skos:historyNote • Some problems: unclear semantics, unclear relationships of replacing concepts (succession, coordination?) • <historyNote rdf:parseType="Resource"> • <dct:isReplacedBy rdf:resource="class/370.15/2007/12"/> • </historyNote> • <historyNote rdf:parseType="Resource"> • <dct:isReplacedBy rdf:resource="class/306.43/1996"/> • </historyNote>

  21. DDC in SKOS: Further Issues • Non-assignable concepts (“node labels”): skos:Collection and skos:member not usable • SKOS somewhat underspecified as RDF vocabulary; much has to be done by following best practice recommendations • SKOS tool stack still rather thin; could change after W3C draft recommendation cools off

  22. Integration into Web Services • Expressing semantic relationships by • Explicit resource description (source: assertion) • Implicit resource description (source: inference) • Application logic, SPARQL patterns • Identified by URIs that are not present in the RDF store, e.g., /ancestors, /children • http://dewey.info/class/338.4/ancestors/about.en.skos • Web service responses • HTTP status codes

  23. Thing Generic Document Service Semantics: Generic Resources • http://dewey.info/class/338.4 • 303 See Other • http://dewey.info/class/338.4/about • [300 Multiple Choices] • application/rdf+xml wins • text/html wins • content negotiation • 200 OK HTML RDF • Content-Location:http://dewey.info/class/338.4/about.de.skos • http://dewey.info/class/338.4/about.de.html

  24. Service Semantics: Blunt Instruments Resource Resource • describes • describes • describes IR • ? • specifies • specifies IR1 IR2 • isVariationOf IR1 IR2 • (Could be made explicit with RDF statements)

  25. Thank you! • Michael Panzer <mailto:panzerm@oclc.org>

  26. RDF model: Gathering assertions about resources • Not everything has to be kept in one “record” in RDF • Reconstructing the whole concept graph for an RI term with SPARQL: • DESCRIBE <http://dewey.info/index/Job%20training>

  27. RDF model: Gathering assertions about a resource • Resulting graph (in Turtle): • @prefix skos: <http://www.w3.org/2008/05/skos#> . • @prefix ddc: <http://dewey.info/schema-terms/> . • <http://dewey.info/index/Job%20training> a skos:Concept ; • skos:inScheme <http://dewey.info/index/2007/12> ; • skos:prefLabel "Job training"@en ; • ddc:isIndexTermOf <http://dewey.info/class/370.113/2007/12> ; • skos:related <http://dewey.info/index/Vocational%20education> .

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