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Linked Open Vocabularies – the vision and the reality

Pierre-Yves VandenbusscheLead ResearcherFujitsu Ireland

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Linked Open Data / Linked Open Vocabularies

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Focus is on linking instances Direct benefit for end applications

(data mashup, knowledge graph, etc.)

Link type owl:sameAs (23.000k) skos:closeMatch (380k) skos:exactMatch (150k) skos:relatedMatch (125k) skos:broadMatch (7k) skos:narrowMatch (1k)

Linked Open Data

Source: http://stats.lod2.eu/

Source: http://lod-cloud.net

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Focus is on linking schema elements Facilitates data linkage Enables multi vocabularies

ontology design

Link type (% of vocabularies in LOV with this relationship) voaf:metadataVoc (87%) voaf:specializes (55%) voaf:extends (51%) voaf:hasEquivalences With (15%) voaf:generalizes (6%) voaf:hasDisjunctionsWith (3%)

Linked Open Vocabularies

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Towards a Linked Open Vocabularies ecosystem

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Towards a Linked Open Vocabularies ecosystem

History Started 2011-Q1 (Initially a deliverable of Datalift project :

http://datalift.org) 2012 : Growing interest beyond the initial scope

Migration to OKFN since July 2012 : http://lov.okfn.org

Status as of June 2014 440 vocabularies and counting 429 agents involved (342 foaf:Person and 87 foaf:Organization) Continuous feedback from the community (subscribe to the

Google+ community)

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Towards a Linked Open Vocabularies ecosystem

LOV Home : http://lov.okfn.org LOV-Search : http://lov.okfn.org/dataset/lov/search/ LOV-Suggest : http://lov.okfn.org/dataset/lov/suggest/ LOV-Stats : http://lov.okfn.org/dataset/lov/stats/ LOV-API : http://lov.okfn.org/dataset/lov/apidoc/ LOV-Bot : Daily or on-demand scan of vocabularies LOV-Edit : Administration and curation back-office SPARQL endpoint(s) / Dump

Endpoint: http://lov.okfn.org/endpoint/lov_aggregator Nquads: http://lov.okfn.org/dataset/lov/agg/lov_aggregator.nq.zip

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Towards a Linked Open Vocabularies ecosystem

Rich metadata

Relations with other

vocabularies

Versions and timeline

Source: http://lov.okfn.org/dataset/lov/details/vocabulary_org.html

Usage in linked data

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Typology of vocabulary linkage

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Before linking your vocabularies

Pros Maximising the probability that data can be consumed by applications

without requiring further pre-processing of the data or modification of the application

Facilitating the creation of links between different datasets entities using same or related types/properties.

Easing data understanding by linking to already well known vocabularies

Cons Meaning Dependency to external specifications beyond our control and

with unknown futures. Meaningfulness of linkage between two models with different intentions

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Vocabulary linkage

Source: http://lov.okfn.org/vocab/voaf/

<http://purl.org/vocommons/voaf> dc:modified “2013-05-24”^^xsd:Date

voaf:metadataVocmetadata vocabulary - Indicates that the subject vocabulary uses the object vocabulary in metadata at vocabulary or element level

CONSTRUCT{ ?vocab1 voaf:metadataVoc ?vocab2}WHERE{ ?elem1 ?elem2 ?o. ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

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Vocabulary linkage

voaf:extendsextends - Indicates that the subject vocabulary extends the expressivity of the object vocabulary by declaring subsumption relationships, using object vocabulary class as domain or range of a subject vocabulary property, defining local restrictions etc ...

CONSTRUCT{ ?vocab1 voaf:extends ?vocab2}WHERE{{?elem1 owl:inverseOf ?elem2. FILTER(!isBlank(?elem2))} UNION{?elem1 rdfs:domain ?elem2. FILTER(!isBlank(?elem2))} UNION{?elem1 rdfs:range ?elem2. FILTER(!isBlank(?elem2))} ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

mo:biography rdfs:range foaf:Document

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Vocabulary linkage

voaf:specializesspecializes - Indicates that the subject vocabulary defines some subclasses or subproperties of the object vocabulary, or local restrictions on those.

CONSTRUCT{ ?vocab1 voaf:specializes ?vocab2}WHERE{ {?elem1 rdfs:subPropertyOf ?elem2. FILTER(!isBlank(?elem2))} UNION{?elem1 rdfs:subClassOf ?elem2. FILTER(!isBlank(?elem2))} UNION{?elem1 skos:broadMatch ?elem2. FILTER(!isBlank(?elem2))} ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

cgov:fullTimeEquivalentSalary rdfs:subPropertyOf org:remuneration

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Vocabulary linkage

voaf:generalizesgeneralizes - Indicates that the subject vocabulary generalizes by some superclasses or superproperties the object vocabulary.

CONSTRUCT{ ?vocab1 voaf:generalizes ?vocab2}WHERE{ {?elem1 skos:narrowMatch ?elem2. FILTER(!isBlank(?elem2))} UNION{?elem2 rdfs:subPropertyOf ?elem1.} UNION{?elem1 a owl:Class. ?elem1 owl:unionOf ?union. ?union rdf:first ?elem2.} UNION{ […]} FILTER(!isBlank(?elem2)) ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

ldr:RightsExpression skos:narrowMatch cc:License

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How to link two vocabularies

voaf:hasEquivalencesWithhas equivalences with - Indicates that the subject vocabulary declares some equivalent classes or properties with the object vocabulary.

CONSTRUCT{ ?vocab1 voaf:hasEquivalencesWith ?vocab2}WHERE{ {?elem1 owl:equivalentProperty ?elem2.} UNION{?elem1 owl:sameAs ?elem2.} UNION{?elem1 owl:equivalentClass ?elem2.} UNION{?elem2 owl:equivalentProperty ?elem1.} UNION{?elem2 owl:equivalentClass ?elem1.} UNION{?elem1 skos:exactMatch ?elem2.} UNION{?elem2 skos:exactMatch ?elem1.} FILTER(!isBlank(?elem2)) ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

bio:child owl:equivalentProperty rel:parentOf

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Vocabulary linkage

voaf:hasDisjunctionsWithhas disjunctions with - Indicates that the subject vocabulary declares some disjoint classes with the object vocabulary.

CONSTRUCT{ ?vocab1 voaf:hasDisjunctionsWith ?vocab2}WHERE{ ?elem1 owl:disjointWith ?elem2. FILTER(!isBlank(?elem2)) ?elem1 rdfs:isDefinedBy ?vocab1. ?vocab1 a voaf:Vocabulary. ?elem2 rdfs:isDefinedBy ?vocab2. ?vocab2 a voaf:Vocabulary. FILTER(?vocab1!=?vocab2)}

skosxl:Label owl:disjointWith skos:Concept

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Maintenance cost of links in a distributed system Sync with new version in external vocabularies

Find existing vocabularies / concept schemes

Map vocabularies Handle language heterogeneity

Discussion

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