Linked Data is a term used to describe a method of exposing, sharing, and connecting data on the Semantic Web. The practice emphasizes Web access to data using existing Web technologies such as URIs and HTTP. It also emphasizes links between related Web resources.
Tim Berners-Lee outlined four principles of Linked Data in his 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.
Linked Data is made available on the Web using the Resource Description Framework (RDF), a flexible data model for publishing, and integrating heterogeneous data on the Web. RDF model instance data can be serialized in a number of ways en route to publishing data on the web, formats include: RDFa (RDF in HTML attributes) XML, Notation 3 (N3), Turtle (terse RDF triple language) and others.
Linking Open Data Community Project
The goal of the W3C Semantic Web Education and Outreach group's 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.
- DBpedia - a dataset containing extracted data from Wikipedia; it contains about 1.6 million concepts described by 91 million triples, including abstracts in 10 different languages
- 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.
- Revyu - a Review service consumes and publishes Linked Data, primarily from DBpedia.
- riese - serving statistical data about 500 million Europeans (the first linked dataset deployed with XHTML+RDFa)
Use Case Demos
- Linked Data Web architecture note by Tim Berners-Lee
-  The Linked Data community Wiki
-  List of public Linked Open Data sources
- Tutorial: How to publish Linked Data on the Web
- White Paper: How to publish Linked Data on the Web using OpenLink Virtuoso
- Linked Data: Principles and State of the Art - Chris Bizer, Tom Heath, Tim Berners-Lee at WWW2008
- Native to a Web of Data - Tom Coates
- Deploying Linked Data using OpenLink Virtuoso
- The Linking Open Data Project - Bootstrapping the Web of Data - Tom Heath