RDF (Resource Description Framework) is a W3C standard for expressing relationships between web resources. RDF triples consist of subject-predicate-object. Resources are typically identified by URIs; values can be literal or other URIs. RDF data is structured in graphs and used for machine-readable metadata, linked data, and semantic web. Queries are executed using SPARQL. Main serialization formats include RDF/XML, Turtle, N-Triples, JSON-LD