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DDC, SKOS, and Linked Data on the Web

Overview. Why transform the DDC into a SKOS vocabulary?Creating URIsWhat is a concept?What is an information resource?Analyzing DDC for modeling in RDF/SKOSIdentifying conceptsAligning DDC elements with SKOS classes and propertiesModeling sematic relationshipsIntegration into RESTful web ser

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DDC, SKOS, and Linked Data on the Web

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

    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 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

    10. Analyzing DDC for modeling in RDF/SKOS 370.113 Vocational 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

    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 .

    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> Switching to RDF/XML for demonstration: RDF is a data model without a fixed serialization. We have seen Turtle/N3 up to now, here we are seeing records in the much maligned RDF/XML (incomplete; without prefix and base declarations).Switching to RDF/XML for demonstration: RDF is a data model without a fixed serialization. We have seen Turtle/N3 up to now, here we are seeing records in the much maligned RDF/XML (incomplete; without prefix and base declarations).

    16. RDF model: Gathering assertions about a resource Could be obtained by using DESCRIBE in SPARQL.Could be obtained by using DESCRIBE in SPARQL.

    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. Service Semantics: Generic Resources http://dewey.info/class/338.4

    24. Service Semantics: Blunt Instruments

    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> Or, alternatively by using CONSTRUCT: CONSTRUCT <http://dewey.info/index/Job%20training> ?p ?o WHERE { <http://dewey.info/index/Job%20training> ?p ?$o } Or, alternatively by using CONSTRUCT: CONSTRUCT <http://dewey.info/index/Job%20training> ?p ?o WHERE { <http://dewey.info/index/Job%20training> ?p ?$o }

    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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