Linked data

What is Linked Data?

Linked data is a method for publishing structured data using vocabularies like schema.org that can be connected together and interpreted by machines.

Using linked data, statements encoded in triples can be spread across different websites. On Website A we can present the entity Jason and the fact that he knows Marie. On website B we can provide all the information about Marie  and on the Website C we can find information about Marie’s birthplace.

Linked Data - Sharing Knowledge

Each page contains the structured data to describe an entity and the link to the entity that could be described on a different website.

Back in 2006 Tim Berners-Lee described linked data as follows:

The Semantic Web isn’t just about putting data on the web. It is about making links, so that a person or machine can explore the web of data.  With linked data, when you have some of it, you can find other, related, data.

In computing linked data describes a method of publishing and linking data coming from heterogeneous data sources that can be interlinked and shared.

Linked Data 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.

Queries over linked data are made using a semantic query language called SPARQL that allows to retrieve and manipulate data stored in Resource Description Framework (RDF) format.

Linked Data Explained

This great introduction video on linked data, the Google Knowledge Graph and Facebook Open Graph protocol was done by @manusporny.

Why is it Important to Publish 5-stars Linked Data?

There are four simple principles to follow when publishing data on the web (and yes, structured data is open data as it is fully accessible).

  1. Use URIs as names for things (this is the unique identifier that we introduced above)
  2. Use HTTP URIs so that people can look up those names (this means that the ID of every entity shall be accessible via HTTP URI)
  3. When someone looks up a URI, provide useful information, using the standards (Behind these URIs we need to publish data using a linked data standard called RDF)
  4. Include links to other URIs. so that they can discover more things (and here is where we need to add owl:sameAs property).

To simplify a 5-stars open dataset is simply a way to publish metadata (using linked data standard) that makes it readable and accessible by machines.

That is why by connecting a piece of text, written by a human with an open dataset created by a machine, our content becomes fully accessible and machine-friendly.

Some of the primary datasets that implement the 5-stars linked data schema are foundational for the machine learning algorithms behind semantic search engines like Google and Bing as well as digital personal assistants like Alexa, Cortana, and the Google Assistant.

These datasets (like DBpedia, Wikidata, Geonames just to name it a few) are all interlinked together to form a Linked Open Data Cloud.

LOD Cloud

When you add structured data to your WordPress website using a plugin like WordLift, that structured data gets published as open linked data. In short, your WordPress website, and the metadata of your own content becomes part of that Linked Open Data Cloud. Thus by adding an additional layer to the Semantic Web your WordPress website also becomes part of it!