Resource Description Framework (RDF)

sounderslipInternet and Web Development

Oct 22, 2013 (3 years and 9 months ago)

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Resource Description Framework (RDF)


RDF is a data modelling framework for describing “resources”



A “resource” can be anything at all



Resources have unique identifiers called Uniform Resource Identifiers
(URI)


Resources

Two kinds of resources in RDF:


Information resources

Web pages, videos, etc. Things you can download off the web.


Non
-
information resources

People, abstract concepts, places, types of relationships between things,
etc)


RDF is made out of “triples”


Triples link two things (subject and object) together, via a third thing (a
“predicate”
)


The things are either:


“resources” identified by a “URI”


“literal” values such as numbers, pieces of text, dates, etc.







RDF “triples”

:Work

On Our Selection

On Our Selection (1912) is
a theatrical adaptation of
On Our Selection! (1899).


title

abstract

Subject

Predicate

Object

:Work

title

On Our Selection

:Work

abstract

On Our Selection
(1912) is a
theatrical
adaptation of On
Our Selection!
(1899).


RDF “graphs”


A collection of triples is a “graph”



“Graph” is used in a specific sense:


a set of nodes, connected together by
lines


= a “network”




XML (Extensible
Markup

Language)


RDF is an abstract model


RDF graphs can be “serialized” using a variety of syntaxes


XML syntax is commonly used for serializing RDF



<?xml version="1.0" encoding="UTF
-
8"?>

<
rdf:RDF


xmlns:rdf
="http://www.w3.org/1999/02/22
-
rdf
-
syntax
-
ns#"

xmlns:dcterms
=“http://
purl.org
/dc/terms/”


xmlns:dc
=“”
>

<
rdf:Description

rdf:about
=“http
://
www.austlit.edu.au/run?ex
=
ShowWork&workId
=C1@
)”
>


<
dc:title
>
On
Our
Selection
</
dc:title
>


<
dcterms:abstract
>
On
Our Selection (1912) is a theatrical adaptation of On
Our Selection! (1899
)
</
dcterms:abstract
>

</
rdf:Description
>

</
rdf:RDF
>

Alternate syntaxes e.g. Turtle

@prefix

austlit
:
<http://www.austlit.edu.au/run?ex=
ShowWork&workI
d
=>


austlit:C1
@
)
dc:title

"
On Our
Selection”;


dcterms:abstract

"
On Our Selection (1912) is a
theatrical adaptation of On Our Selection! (1899
)”.

RDF “
ontologies



An ontology is essentially a formalised technical
vocabulary


Described using RDF Schema & Web Ontology Language
(OWL)


Each term in the vocabulary is a “resource”, and an ontology is
usually published as a graph of those resources
.


Vocabularies may themselves be
standardised



e.g. Dublin Core


There are bibliographic
ontologies
, biographical
ontologies
,
scientific, geographic, etc, etc.





Linked Data
-

the technique


Linked Data is a technique for publishing RDF as graphs on the WWW.


Some of the
URIs

in an RDF graph refer to information resources; you can
retrieve those resource in your browser.


You can't, however, download a person or a concept.


If you
try

to download a non
-
information resource from a Linked Data
web server, it will redirect you an information resource (which could be
an RDF graph, for instance), that contains information about that non
-
information resource.


An exploratory, “follow your nose” technique for discovering data

Linked Data



the

principles


Use
URIs

for identifiers


Use de
-
referenceable

HTTP
URIs

(rather than
URNs
)


Use semantic web standards (e.g. RDF, SPARQL)


Include links to related resources to create a ‘web of data’

Linked Open Data
-

the movement


Linked Open Data is a growing movement


More and more data custodians are publishing in this way


Breaks down silos and allows interlinking


Third parties can enhance others' datasets


Third parties can link others' datasets together


Collaboratively building a Linked Data Cloud!