DDC, SKOS, and Linked Data on the Web

OCLC/ISKO-NA Preconference

5 August 2008

Michael PanzerGlobal Product Manager, Taxonomy ServicesOCLC

DDC, SKOS, and Linked Data on the Web

DDC, SKOS, and Linked Data on the Web

OverviewOverview

1. Why transform the DDC into a SKOS vocabulary?

2. Creating URIs

1. What is a concept?

2. What is an information resource?

3. Analyzing DDC for modeling in RDF/SKOS

1. Identifying concepts

2. Aligning DDC elements with SKOS classes and properties

3. Modeling sematic relationships

4. 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

1. Design of identifiers

2. Design of verbal designators (“verbal plane”)

3. Data representation

4. Vocabulary enhancement

5. User contribution

6. Versioning

7. 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 URIsExample 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 URIsExample 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/SKOSAnalyzing 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)


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

Career development

Career education

Education of employees

Employee development

Human resource development …

Career education

Career education--United States

Career education--United States--Curricula

Core competencies

…

Vocational education

Vocational training centers

Relative Index

Mapped LCSH

skos:relatedMatch

skos:relatedMatch


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

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> .


<class/370.113/2007/12> skos:relatedMatch

<http://tspilot.oclc.org/lcsh/sh%2085020255%20> ,



<http://tspilot.oclc.org/lcsh/sh%2096002453%20> .


<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> .


@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 TermsRDF 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>

RDF model: Gathering assertions about a resourceRDF model: Gathering assertions about a resource

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 eventsModeling 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>


<dct:isReplacedBy rdf:resource="class/306.43/1996"/>

</historyNote>

</Concept>

Simple relocation/discontinuationSimple relocation/discontinuation

- Two different representations of concept history modeled by skos:historyNote

- Some problems: unclear semantics, unclear relationships of replacing concepts (succession, coordination?)


<dct:isReplacedBy rdf:resource="class/370.15/2007/12"/>

</historyNote>


<dct:isReplacedBy rdf:resource="class/306.43/1996"/>

</historyNote>

DDC in SKOS: Further IssuesDDC 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 ServicesIntegration 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 ResourcesService Semantics: Generic Resources

http://dewey.info/class/338.4

http://dewey.info/class/338.4/about

Thing

Generic Document

303 See Other

RDF HTML

Content-Location:

http://dewey.info/class/338.4/about.de.skoshttp://dewey.info/class/338.4/about.de.html

content negotiation

application/rdf+xml wins text/html wins

200 OK

[300 Multiple Choices]

Service Semantics: Blunt InstrumentsService Semantics: Blunt Instruments

IR1 IR2

Resource

describes

IR

specifies

isVariationOf

specifiesIR1 IR2

Resource

describes

?

describes

(Could be made explicit with RDF statements)

Thank you!Thank you!

Michael Panzer <mailto:[email protected]>

RDF model: Gathering assertions about resourcesRDF 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 resourceRDF 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> .

DDC, SKOS, and Linked Data on the Web

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DDC, SKOS, and Linked Data on the Web