Editing Resource Description Framework (section)

=== Resource identification ===
The subject of an RDF statement is either a [[uniform resource identifier]] (URI) or a [[blank node]], both of which denote [[web resource|resource]]s. Resources indicated by [[blank node]]s are called anonymous resources. They are not directly identifiable from the RDF statement. The predicate is a URI which also indicates a resource, representing a relationship. The object is a URI, blank node or a [[Unicode]] [[string literal]]. 
As of RDF 1.1 resources are identified by [[Internationalized Resource Identifier]]s (IRIs); IRI are a generalization of URI.<ref>{{Cite web |date=25 February 2014 |title=RDF 1.1 Concepts and Abstract Syntax |url=https://www.w3.org/TR/rdf11-concepts/ |url-status=live |archive-url=https://web.archive.org/web/20240114081050/https://www.w3.org/TR/rdf11-concepts/ |archive-date=Jan 14, 2024 |website=W3C}}</ref>

In Semantic Web applications, and in relatively popular applications of RDF like [[RSS (file format)|RSS]] and [[FOAF (software)|FOAF]] (Friend of a Friend), resources tend to be represented by URIs that intentionally denote, and can be used to access, actual data on the World Wide Web. But RDF, in general, is not limited to the description of Internet-based resources. In fact, the URI that names a resource does not have to be dereferenceable at all. For example, a URI that begins with "http:" and is used as the subject of an RDF statement does not necessarily have to represent a resource that is accessible via [[HTTP]], nor does it need to represent a tangible, network-accessible resource—such a URI could represent absolutely anything. However, there is broad agreement that a bare URI (without a # symbol) which returns a 300-level coded response when used in an HTTP GET request should be treated as denoting the internet resource that it succeeds in accessing.

Therefore, producers and consumers of RDF statements must agree on the semantics of resource identifiers. Such agreement is not inherent to RDF itself, although there are some controlled vocabularies in common use, such as Dublin Core Metadata, which is partially mapped to a URI space for use in RDF. The intent of publishing RDF-based ontologies on the Web is often to establish, or circumscribe, the intended meanings of the resource identifiers used to express data in RDF. For example, the URI:
{{pre|<nowiki>http://www.w3.org/TR/2004/REC-owl-guide-20040210/wine#Merlot</nowiki>}}
is intended by its owners to refer to the class of all [[Merlot]] red wines by vintner (i.e., instances of the above URI each represent the class of all wine produced by a single vintner), a definition which is expressed by the OWL ontology—itself an RDF document—in which it occurs.  Without careful analysis of the definition, one might erroneously conclude that an instance of the above URI was something physical, instead of a type of wine.

Note that this is not a 'bare' resource identifier, but is rather a [[Uniform Resource Identifier#URI references|URI reference]], containing the '#' character and ending with a [[fragment identifier]].