The term web resource was first introduced to refer to targets of Uniform Resource Locators (URLs), but its definition has been further extended to include the referent of any Uniform Resource Identifier (RFC 3986), or Internationalized Resource Identifier (RFC 3987). In the Semantic Web, abstract resources and their semantic properties are described using the family of languages based on Resource Description Framework (RDF).

The concept of resource has evolved during the Web history, from the early notion of static addressable document or file, to a more generic and abstract definition, now encompassing every thing or entity that can be identified, named, addressed or handled, in any way whatsoever, in the Web at large, or in any networked information system. The declarative aspects of a resource (identification and naming) and its functional aspects (addressing and technical handling) were not clearly distinct in the early specifications of the Web, and the very definition of the concept has been the subject of long and still open debate involving difficult, and often arcane, technical, social, linguistic and philosophical issues.

References: Wikipedia
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