Linked Data is a method of publishing structured data so that it can be interlinked and become more useful through semantic queries.
Tim Berners-Lee outlined four principles of linked data in his “Linked Data” note of 2006:
• Use URIs to name (identify) things.
• Use HTTP URIs so that these things can be looked up (interpreted, “dereferenced”).
• Provide useful information about what a name identifies when it’s looked up, using open standards such as RDF, SPARQL, etc.
• Refer to other things using their HTTP URI-based names when publishing data on the Web.
Tim Berners-Lee gave a presentation on linked data at the TED 2009 conference. In it, he restated the linked data principles as three “extremely simple” rules:
• All kinds of conceptual things, they have names now that start with HTTP.
• If I take one of these HTTP names and I look it up…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.
• When I get back that information it’s not just got somebody’s height and weight and when they were born, its 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.
Linked Open Data (LOD) is Linked Data which is released under an open licence, which does not impede its reuse for free.
— Tim Berners-Lee, Linked Data