9.2 RDF and ontologies 

RDF: 

∙ RDF stands for Resource Description Framework 

∙ RDF is a framework for describing resources on the web 

∙ RDF is designed to be read and understood by computers 

∙ RDF is not designed for being displayed to people 

∙ RDF is written in XML 

∙ RDF is a part of the W3C's Semantic Web Activity

∙ RDF is a W3C Recommendation from 10. February 2004 

The RDF language is a part of the W3C's Semantic Web Activity. W3C's "Semantic Web  Vision" is a future where: 

∙ Web information has exact meaning 

∙ Web information can be understood and processed by computers 

∙ Computers can integrate information from the web 

RDF uses Web identifiers (URIs) to identify resources. 

RDF describes resources with properties and property values. 

RDF Resource, Property, and Property Value 

RDF identifies things using Web identifiers (URIs), and describes resources with properties and  property values. 

Explanation of Resource, Property, and Property value: 

∙ A Resource is anything that can have a URI, such as "https://www.w3schools.com/rdf" ∙ A Property is a Resource that has a name, such as "author" or "homepage" ∙ A Property value is the value of a Property, such as "Jan Egil Refsnes" or  

"https://www.w3schools.com" (note that a property value can be another resource) Ontologies: 

The Web Ontology Language (OWL) is a family of knowledge representation languages for  authoring ontologies. Ontologies are a formal way to describe taxonomies and classification  networks, essentially defining the structure of knowledge for various domains: the nouns  representing classes of objects and the verbs representing relations between the objects.  Ontologies resemble class hierarchies in object-oriented programming but there are several  critical differences.  

Class hierarchies are meant to represent structures used in source code that evolve fairly slowly  (typically monthly revisions) whereas ontologies are meant to represent information on the  Internet and are expected to be evolving almost constantly. Similarly, ontologies are typically far  more flexible as they are meant to represent information on the Internet coming from all sorts of  heterogeneous data sources. Class hierarchies on the other hand are meant to be fairly static and  rely on far less diverse and more structured sources of data such as corporate databases. n the late 1990s, the World Wide Web Consortium (W3C) Metadata Activity started work on  RDF Schema (RDFS), a language for RDF vocabulary sharing. The RDF became a W3C  Recommendation in February 1999, and RDFS a Candidate Recommendation in March  2000.[19] In February 2001, the Semantic Web Activity replaced the Metadata Activity.[19] In  2004 (as part of a wider revision of RDF) RDFS became a W3C Recommendation.[20] Though  RDFS provides some support for ontology specification, the need for a more expressive ontology  language had become clear.