VoID: Metadata for RDF Datasets

Digital Enterprise Research Institute www.deri.ie

VoID – Metadata for
RDF datasets
Richard Cyganiak, Linked Data Research Centre

Stefan.Decker@deri.org
http://www.StefanDecker.org/

Copyright 2010 Digital Enterprise Research Institute. All rights reserved.


VoID
Vocabulary of Interlinked Datasets

W3C Interest Group note

http://www.w3.org/TR/void/
3


“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 linksetis a collection of such RDF links between two
datasets

voiD schema

Statistics

Interlinking

General metadata

General dataset metadata

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

General dataset metadata

Access metadata

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

Access metadata

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

Describing linksets


Deployment and Discovery

Alongside a dataset


 Publishing aVoIDfile 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 inVoID:
 semantic.ckan.net

Applications

26

Ed Summers’ LOD Graph

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

28

VoID: Metadata for RDF Datasets

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