Linked data

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In computing, linked data describes a method of publishing structured data so that it can be interlinked and become more useful. It builds upon standard Web technologies such as HTTP and URIs, but rather than using them to serve web pages for human readers, it extends them to share information in a way that can be read automatically by computers. This enables data from different sources to be connected and queried.[1]

Tim Berners-Lee, director of the World Wide Web Consortium, coined the term in a design note discussing issues around the Semantic Web project.[2] However, the idea is very old and is closely related to concepts including database network models, citations between scholarly articles, and controlled headings in library catalogs.[citation needed]

Principles

Tim Berners-Lee outlined four principles of linked data in his Design Issues: Linked Data note, paraphrased along the following lines:

  1. Use URIs to identify things.
  2. Use HTTP URIs so that these things can be referred to and looked up ("dereferenced") by people and user agents.
  3. Provide useful information about the thing when its URI is dereferenced, using standard formats such as RDF/XML.
  4. Include links to other, related URIs in the exposed data to improve discovery of other related information on the Web.

Tim Berners-Lee gave a presentation on linked data[3] at the TED 2009 conference. In it, he restated the linked data principles as three "extremely simple" rules:

  1. All kinds of conceptual things, they have names now that start with HTTP.
  2. I get important information back. I will get back some data in a standard format which is kind of useful data that somebody might like to know about that thing, about that event.
  3. I get back that information it's not just got somebody's height and weight and when they were born, it's got relationships. And when it has relationships, whenever it expresses a relationship then the other thing that it's related to is given one of those names that starts with HTTP.

Note that although the second rule mentions "standard formats", it does not require any specific standard, such as RDF/XML.

Components

Linking open-data community project

Instance linkages within the linking open data datasets
Class linkages within the linking open data datasets

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. In October 2007, datasets consisted of over two billion RDF triples, which were interlinked by over two million RDF links. By September 2011 this had grown to 31 billion RDF triples, interlinked by around 504 million RDF links. There is also an interactive visualization of the linked data sets to browse through the cloud.

Dataset instance and class relationships

Clickable diagrams that show the individual datasets and their relationships within the DBpedia-spawned LOD cloud, as shown by the figures to the right, are:

See also

External links

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Datasets

Projects

Use case demos

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Further reading

Browsers

Presentations

Events

References

  1. ^ Bizer, Christian; Heath, Tom; Berners-Lee, Tim (2009). "Linked Data—The Story So Far". International Journal on Semantic Web and Information Systems 5 (3): 1-22. doi:10.4018/jswis.2009081901. ISSN 15526283. http://tomheath.com/papers/bizer-heath-berners-lee-ijswis-linked-data.pdf. Retrieved 2010-12-18. 
  2. ^ Tim Berners-Lee (2006-07-27). "Linked Data—Design Issues". W3C. http://www.w3.org/DesignIssues/LinkedData.html. Retrieved 2010-12-18. 
  3. ^ "Tim Berners-Lee on the next Web". http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html. 
  4. ^ "CORDIS FP7 ICT Projects – LOD2". European Commission. 2010-04-20. http://cordis.europa.eu/fetch?CALLER=PROJ_ICT&ACTION=D&CAT=PROJ&RCN=95562. 
  5. ^ "LOD2 Project Fact Sheet – Project Summary". 2010-09-01. http://static.lod2.eu/Deliverables/LOD2_D12.5.1_Project_Fact_Sheet_Version.pdf. Retrieved 2010-12-18.