Semantic Web
Tim Berners-Lee's proposed extension of the web in which data carries machine-readable meaning via RDF triples, OWL ontologies, and SPARQL queries. Standardized by W3C and partially realized in linked-data and scientific-data ecosystems, but largely supplanted on the open web by schema.org and LLM-based extraction.
The Semantic Web is an extension of the World Wide Web proposed by Tim Berners-Lee in which information carries explicit, machine-readable meaning rather than only human-readable text. The canonical statement of the vision is the May 2001 Scientific American article co-authored with James Hendler and Ora Lassila, which described software agents reasoning over structured web data to handle real-world tasks. The technical stack that grew around it includes RDF (Resource Description Framework, which models data as subject-predicate-object triples), RDF Schema and OWL (Web Ontology Language, for class hierarchies and inference), SPARQL (a query language for triple stores), and serialization formats such as Turtle, RDF/XML, and later JSON-LD. The W3C standardized most of these layers through the 2000s. Adoption in the open web stayed narrow: the entry cost was high, publishers had little incentive, and the lighter schema.org vocabulary captured the SEO market in 2011. The Semantic Web nevertheless became foundational in domains with strong integration needs, including library and museum metadata, biomedical data through projects like Bio2RDF and UniProt, government open data, and Wikimedia's Wikidata. Modern LLMs have absorbed many of the user-facing use cases by extracting structured information from unstructured prose at inference time.