VoID: Metadata for RDF Datasets

Copyright 2010 Digital Enterprise Research Institute. All rights reserved.

Digital Enterprise Research Institute www.deri.ie

VoID – Metadata for RDF datasets

Richard Cyganiak, Linked Data Research Centre

[email protected]://www.StefanDecker.org/


VoIDVocabulary of Interlinked Datasets


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W3C Interest Group note

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“What business-related datasets are in the LOD Cloud?”

“Which datasets deal with politics and transparency in the EU?”

“We have some DERI data. What could we link it to?”


Read …

http://esw.w3.org/TaskForces/CommunityProjects/LinkingOpenData/DataSets


Click …


Sindice …


Google …


And even if we find a dataset …


Standard questions

What kind of data is there? Examples? Is it up to date? Who publishes it? Where is the SPARQL endpoint? Is there a download? How big is it? What’s the license?


Datasets

A dataset is a set of RDF triples that are published, maintained or aggregated by a single provider


Linksets

An RDF link is an RDF triple whose subject and object are described in different datasets

A linkset is a collection of such RDF links between two datasets


voiD schema

General metadata

Interlinking

Statistics


General dataset metadata

Leveraging DublinCore: Dataset homepage Publisher Title and description Categorisation Licensing Technical features


General dataset metadata

:DBpedia a void:Dataset ; dcterms:title "DBPedia” ; dcterms:description "RDF data extracted from Wikipedia” ; dcterms:contributor :FU_Berlin ; dcterms:source <http://dbpedia.org/resource/Wikipedia> ; void:feature <http://www.w3.org/ns/formats/RDF_XML> ; dcterms:modified "2008-11-17"^^xsd:date .

:Geonames a void:Dataset ; dcterms:subject <http://dbpedia.org/resource/Location> .

:GeoSpecies a void:Dataset ; dcterms:license <http://creativecommons.org/licenses/by-sa/3.0/us/> .


Access metadata

How to access the actual RDF triples: SPARQL endpoints RDF data dumps Root resources URI lookup endpoints OpenSearch description documents


Access metadata

:exampleDS void:Dataset ; void:sparqlEndpoint <http://example.org/sparql> ; void:dataDump <http://example.org/dump1.rdf> ; void:uriLookupEndpoint <http://api.example.org/search?qt=term> .


Structural metadata

High-level information about schema and internal structure of a dataset

Can be helpful when exploring or querying datasets Example resources Patterns for resource URIs Vocabularies Dataset partitions Statistics


Structural metadata

:DBpedia a void:Dataset; void:exampleResource <http://dbpedia.org/resource/Berlin> .

:LiveJournal a void:Dataset; void:vocabulary <http://xmlns.com/foaf/0.1/> .

:DBpedia a void:Dataset; void:classPartition [ void:class foaf:Person; void:entities 312000; ]; void:propertyPartition [ void:property foaf:name; void:triples 312000; ]; .


Describing linksets


Describing linksets

:DBpedia a void:Dataset ; void:subset :DBpedia2Geonames .

:Geonames a void:Dataset .

:DBpedia2Geonames a void:Linkset ; void:target :DBpedia ; void:target :Geonames ; void:linkPredicate owl:sameAs .


Deployment and Discovery


Alongside a dataset


Publishing a VoID file alongside a dataset Turtle RDFa

Discovery (well-known URI) http://yoursite/.well-known/void


Users

Used by DBpedia, OpenLink, data.gov.uk, … 30% of LOD datasets have VoID metadata The entire LOD Cloud described in VoID:

semantic.ckan.net


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Applications


Ed Summers’ LOD Graph


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Summary

Metadata for linked datasets For the 4-5 star datasets W3C Interest Group note (VoID 2)

http://www.w3.org/TR/void/ Leverages Dublin Core, FOAF, etc. Used by DBpedia, OpenLink, data.gov.uk, … Used to generate the LOD Cloud diagram The entire LOD Cloud described in VoID:

semantic.ckan.net

http://www.w3.org/TR/void/

Technology

VoID: Metadata for RDF Datasets