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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

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!

  • Michael Panzer <mailto:panzerm@oclc.org>


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> .