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RDF
RDF stands for
Resource Description Framework and is the main technology for the
Semantic Web .
RDF is intended to give a simple means for making statements about resources . A resource can be anything and is identified by an URI (which is guaranteed to be globally unique).
RDF tries to capture information in subject-predicate-object triples.
Triplet
An
RDF triplet is a statement with
one subject (which is an IRI or a blank node)
one predicate (which is an IRI)
one object (which is an IRI, (date-type) literal or blank node)
The subject and object can be thought of a node , the predicate as a directed edge that connnects these nodes.
The same IRI might function as both a node or predicate in the same graph.
IRIs, literals and blank nodes are also referred to as RDF terms .
IRI
An IRI is a
Unicode string that corresponds to the syntax defined in
RFC 3987 . An IRI is absolute and may contain a fragment identifier.
Graph
An RDF graph is a set of triplets.
Datasets
An RDF dataset is a collection of RDF graphs.
One of these graphs is (an unnamed) default graph .
The other graphs have a unique name.
The default graph may be empty.
RDF Document
An RDF document contains («encodes») a a graph or dataset an a concrete RDF syntax .
RDF syntaxes that are able to semantically store graphs or datasets include
RDF Vocabulary
An RDF vocabulary provides a set of IRIs which are intended to be used in graphs.
Typically, the IRIs of a vocabulary start with the same substring. This substring is referred to as namespace IRI .
Namespace IRIs can then be associated with a namespace prefix .
Literals
A literal corresponds to a fixed value of and consists of at least two elements:
A Unicode string that stores the value in lexical form
A datatype-IRI that specifies how the lexical form is interpreted
If the datatype-IRI is http://www.w3.org/1999/02/22-rdf-syntax-ns#langString, the literal also has a language tag.
These literals are referred to as language-tagged strings . (See also rdf:langString).
Data types
XML Schema built-in data types
XML Schema built-in data types have the form http://www.w3.org/2001/XMLSchema#*
Links
prefix.cc : namespace lookup for RDF developers.