Metadata and the Semantic Web - Web Standards: Mastering HTML5, CSS3, and XML - page 233

Linked Open Data
Linked Data (also known as Linking Data ) can be applied to improve the exploitation of the “Web of data.” The expression
refers to the publishing of structured data in a way that typed links are created between data from different sources [19] to
provide a higher level of usability. By using Linked Data, it is possible to find other, related datasets. Structured data should
meet four requirements to be called Linked Data [20]:

• URIs should be assigned to all entities of the dataset.

• HTTP URIs are required to ensure that all entities can be referenced and cited by users

and user agents.

• Entities should be described using standard formats such as RDF/XML.

• Links should be created to other, related entity URIs.

All data that fulfill these requirements and are released for the public are called Linked Open Data (LOD).
The variety of datasets published as Linked Data is represented by the LOD cloud diagram (Figure 7-1 ) [21].

Figure 7-1. The LOD cloud diagram (courtesy of Max Schmachtenberg, Christian Bizer, Anja Jentzsch, and Richard
Cyganiak)