In computing, linked data (often capitalized as 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.
Linked data may also be open data, in which case it is usually described as linked open data (LOD).
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:
- 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.
- Structured data using controlled vocabulary terms and dataset definitions expressed in Resource Description Frameworkserialization formats such as RDFa, RDF/XML, N3, Turtle, or JSON-LD
- Linked Data Platform
Linked open data are linked data that are open data. Tim Berners-Lee gives the clearest definition of linked open data in differentiation with linked data.
Linked Open Data (LOD) is Linked Data which is released under an open license, which does not impede its reuse for free.— Tim Berners-Lee, Linked Data