Vision
Tim Berners-Lee defines the Semantic Web as
The Semantic Web is not a separate Web but an extension of the current one, in which information is given well-defined meaning, better enabling computers and people to work in cooperation
According to the W3C, the concept can be defined as
Semantic Web is the idea of having data on the Web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration, and reuse of data across various applications
Several technologies were developed and standardized with the goal to achieve this vision: RDF, URIs.
Vocabularies, schemas and ontology languages are built on top of RDF and URIs (such as RDF-Schema, OWL and SKOS).