Linked Open Data

In computing, linked data is structured data which is interlinked with other data so it becomes more useful through semantic queries. It builds upon standard Web technologies such as HTTP, RDF and URIs, but rather than using them to serve web pages only for human readers, it extends them to share information in a way that can be read automatically by computers. Part of the vision of linked data is for the Internet to become a global database.

Tim Berners-Lee, director of the World Wide Web Consortium (W3C), coined the term in a 2006 design note about the Semantic Web project.

Linked data may also be open data, in which case it is usually described as Linked Open Data.

Principles

In his 2006 "Linked Data" note, Tim Berners-Lee outlined four principles of linked data, paraphrased along the following lines:
#Uniform Resource Identifiers (URIs) should be used to name and identify individual things.
#HTTP URIs should be used to allow these things to be looked up, interpreted, and subsequently "dereferenced".
#Useful information about what a name identifies should be provided through open standards such as RDF, SPARQL, etc.
#When publishing data on the Web, other things should be referred to using their HTTP URI-based names.

Tim Berners-Lee later restated these principles at a 2009 TED conference, again paraphrased along the following lines:
#All conceptual things should have a name starting with HTTP.
#Looking up an HTTP name should return useful data about the thing in question in a standard format.
#Anything else that that same thing has a relationship with through its data should also be given a name beginning with HTTP.

Components

Thus, we can identify the following components as essential to a global Linked Data system as envisioned, and to any actual Linked Data subset within it:

* URIs
* HTTP
* Structured data using controlled vocabulary terms and dataset definitions expressed in Resource Description Framework serialization formats such as RDFa, RDF/XML