Linked Data

Linked Data is a term used to describe a method of exposing, sharing, and connecting data on the Web via dereferenceable URIs.

Principles

Tim Berners-Lee outlined four principles of Linked Data in his [http://www.w3.org/DesignIssues/LinkedData.html Design Issues: Linked Data] note, paraphrased along the following lines:

* Use URIs to identify things that you expose to the Web as resources.
* Use HTTP URIs so that people can locate and look up (dereference) these things.
* Provide useful information about the resource when its URI is dereferenced.
* Include links to other, related URIs in the exposed data as a means of improving information discovery on the Web.

Components

* URIs (specifically, of the dereferenceable variety)
* HTTP
* Resource Description Framework (RDF)
* Serialization formats (RDFa, RDF/XML, N3, Turtle, and others)

Linking Open Data Community Project

The goal of the W3C Semantic Web Education and Outreach group's [http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/LinkingOpenData Linking Open Data] community project is to extend the Web with a data commons by publishing various open datasets as RDF on the Web and by setting RDF links between data items from different data sources. As of October 2007, datasets consist of over two billion RDF triples, which are interlinked by over two million RDF links.

Examples

Data Sets

* DBpedia - a dataset containing extracted data from Wikipedia; it contains about 2.18 million concepts described by 218 million triples, including abstracts in 11 different languages
* [http://www4.wiwiss.fu-berlin.de/dblp/ DBLP Bibliography] - provides bibliographic information about scientific papers; it contains about 800,000 articles, 400,000 authors, and approx. 15 million triples
* GeoNames provides RDF descriptions of more than 6,500,000 geographical features worldwide.
* [http://revyu.com/ Revyu] - a Review service consumes and publishes Linked Data, primarily from DBpedia.
* [http://riese.joanneum.at riese] - serving statistical data about 500 million Europeans (the first linked dataset deployed with XHTML+RDFa)
* [http://www.umbel.org UMBEL] - a lightweight reference structure of 20,000 subject concept classes and their relationships derived from OpenCyc, which can act as binding classes to external data; also has links to 1.5 million named entities from DBpedia and [http://www.mpi-inf.mpg.de/~suchanek/downloads/yago/ YAGO]

Use Case Demos

* [http://demo.openlinksw.com/Northwind/Customer/ALFKI Data from Northwind SQL Schema as Linked Data]

See also

* Open Data

External links

Further reading

* [http://www.w3.org/DesignIssues/LinkedData.html Linked Data] Web architecture note by Tim Berners-Lee
* [http://esw.w3.org/topic/LinkedData] Linked Data at the ESW Wiki
* [http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/LinkingOpenData/ Linking Open Data project wiki home page]
* [http://esw.w3.org/topic/TaskForces/CommunityProjects/LinkingOpenData/DataSets List of public Linked Data sources]
* [http://linkeddata.org LinkedData.org]
* [http://community.linkeddata.org/ Linked Data Community site]
* Tutorial: [http://sites.wiwiss.fu-berlin.de/suhl/bizer/pub/LinkedDataTutorial/ How to publish Linked Data on the Web]
* White Paper: [http://virtuoso.openlinksw.com/Whitepapers/html/VirtLinkedDataDeployment.html How to publish Linked Data on the Web using OpenLink Virtuoso]
* [http://www2008.org/papers/pdf/p1265-bizer.pdf Linked Data on the Web] - Chris Bizer, Tom Heath, Kingsley Idehen, Tim Berners-Lee. In Proceedings WWW2008, Beijing, China.
* [http://sites.wiwiss.fu-berlin.de/suhl/bizer/pub/LinkingOpenData.pdf Interlinking Open Data on the Web] - Chris Bizer, Tom Heath, Danny Ayers, Yves Raimond. In Proceedings Poster Track, ESWC2007, Innsbruck, Austria.

Presentations

* [http://www.w3.org/2008/Talks/WWW2008-W3CTrack-LOD.pdf Linked Data: Principles and State of the Art] - Chris Bizer, Tom Heath, Tim Berners-Lee at WWW2008
* [http://www.plasticbag.org/archives/2006/02/my_future_of_web_apps_slides/ Native to a Web of Data] - Tom Coates
* [http://virtuoso.openlinksw.com/presentations/Virtuoso_Deploying_Linked_Data/Virtuoso_Deploying_Linked_Data.html Deploying Linked Data] using OpenLink Virtuoso
* [http://linkeddata.org/slides/2008-02-amsterdam-catch.pdf The Linking Open Data Project - Bootstrapping the Web of Data] - Tom Heath

Events

* [http://events.linkeddata.org/ldow2008/ Workshop on Linked Data on the Web (LDOW2008) at WWW2008]
* [http://www.linkeddataplanet.com LinkedData Planet 2008 conference in New York City]

Browsers

* [http://www.w3.org/2005/ajar/tab The Tabulator - Generic data browser and editor.]
* [http://demo.openlinksw.com/DAV/JS/rdfbrowser/index.html OpenLink RDF Browser]
* [http://dataviewer.zitgist.com/ Zitgist DataViewer - Linked Data Viewer]
* [http://www4.wiwiss.fu-berlin.de/bizer/ng4j/disco/ Disco - Hyperdata Browser - A simple browser for navigating the Semantic Web.]
* [http://isweb.uni-koblenz.de/Research/lena/ LENA - a Fresnel LEns based RDF/Linked Data NAvigator with SPARQL selector support.]