W3C Technologies: a Key for Interoperability - slide "Namespaces: a key in peer-to-peer architecture"

RDF supports the use of conventions that:
- will facilitate modular interoperability among separate metadata element sets
- include standard mechanisms for representing semantics that are grounded in its simple, yet powerful, data model
RDF provides for publishing both human-readable and machine-processable vocabularies
(set of properties, or metadata elements, defined by resource description communities)
The ability to standardize the declaration of vocabularies is anticipated to encourage the reuse and extension of semantics among disparate information communities.
RDF uniquely identifies properties using namespaces, that provide a way to unambiguously identify semantics and rules governing properties usage specifying the authority managing the vocabularies.

Example: Dublin Core Initiative defines the "Subject and Keywords" as:

Name:	Subject and Keywords
  Identifier:	Subject
  Definition:	The topic of the content of the resource.
  Comment:	Typically, a Subject will be expressed as keywords, key phrases or classification codes 
	that describe a topic of the resource.
	Recommended best practice is to select a value from a controlled vocabulary or formal classification scheme.