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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

DDC, SKOS, and Linked Data on the Web

Michael Panzer

Global Product Manager, Taxonomy Services

OCLC

overview
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)
why transform the ddc into a skos vocabulary
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!
checklist webification of kos
[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
cool uris for the ddc lightning overview
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
example uris
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
example uris1
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
analyzing ddc for modeling in rdf skos
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)
analyzing ddc for modeling in rdf skos1
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 …

analyzing ddc for modeling in rdf skos2
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
rdf model class 1
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> .
rdf model class 2
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> .
rdf model class 3
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> .
rdf model class 0
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

rdf model relative index terms
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>
modeling concept history events
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
modeling concept history events1
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)
simple relocation discontinuation
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>
simple relocation discontinuation1
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>
ddc in skos further issues
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
integration into web services
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
service semantics generic resources

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
service semantics blunt instruments
Service Semantics: Blunt Instruments

Resource

Resource

  • describes
  • describes
  • describes

IR

  • ?
  • specifies
  • specifies

IR1

IR2

  • isVariationOf

IR1

IR2

  • (Could be made explicit with RDF statements)
thank you
Thank you!
rdf model gathering assertions about resources
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>
rdf model gathering assertions about a resource1
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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