A First Course in RDF and RDFS (Resource Description Framework and Resource Description Framework Schema)

Introduction to RDF and RDFS Mark Birbeck http://webBackplane.com/mark-birbeck

RDF...a four letter word

RDF/XML is the real villain

The promise of XML

RDF Documents

Primer

Concepts

Syntax

Semantics

Vocabulary

Test cases

This tutorial

Concepts

Transporting RDF

Storing

Some sources of RDF data

Querying

Defining vocabularies

Metadata: data about data

Getting data from the web is easy...getting metadata is hard

XML was supposed to give us this information

<music genre="classical">

<title>

The Well-tempered Clavier

</title>

<composer>J. S. Bach</composer>

</music>

Why has XML not delivered?

<document type="classical music">

<name>

</name>

<author>J. S. Bach</author>

</document>

We want to say: "give me everything created by J. S. Bach"

To achieve that we need to agree how to say ' created by ' in any document

Dublin, Ohio Photo by Sleestak66: http://www.flickr.com/people/kesselring/

DC.Creator = "J. S. Bach"

DC.Title = "The Well Tempered Clavier"

abstract

audience

contributor

creator

description

publisher

rightsHolder

...and many more

Often called a vocabulary or taxonomy

<html>

<head>

<title>

Bach: The Well Tempered Clavier

</title>

<meta name=" DC.Title "

content="The Well Tempered Clavier" />

<meta name=" DC.Creator "

content="J. S. Bach" />

</head>

<body>

...

</body>

</html>

<html>

<head>

<title>

An introduction to RDF

</title>

<meta name=" title "

content="Introduction to RDF" />

<meta name=" author "

content="Mark Birbeck" />

</head>

<body>

...

</body>

</html>

<html>

<head>

<title>

An introduction to RDF

</title>

content="Introduction to RDF" />

content="Mark Birbeck" />

</head>

<body>

...

</body>

</html>

<title>

</title>

<composer>J. S. Bach</composer>

</music>

<name>

</name>

<author>J. S. Bach</author>

</document>

<title>

</title>

< dc:creator >J. S. Bach</ dc:creator >

</music>

<name>

</name>

< dc:creator >J. S. Bach</ dc:creator >

</document>

Recap

XML doesn't help

Having unique identifiers does

Unique identifiers are a key concept in RDF

DC.Creator DC.Title

http://purl.org/dc/terms/ creator http://purl.org/dc/terms/ title

Resource Description Framework

http://purl.org/dc/terms/ creator http://purl.org/dc/terms/ title

Recap

Resources and unique identifiers are fundamental for RDF:

http://purl.org/dc/terms/creator http://purl.org/dc/terms/title http://dbpedia.org/resource/Johann_Sebastian_Bach http://dbpedia.org/resource/Well-Tempered_Clavier

Triples

<html>

<head>

<title>

Bach: The Well Tempered Clavier

</title>

content="The Well Tempered Clavier" />

content="J. S. Bach" />

</head>

<body>

...

</body>

</html>

var piece = { title : "The Well-tempered Clavier", creator : "J. S. Bach" };

Triples are sometimes called statements:

J. S. Bach composed "The Well Tempered Clavier". J. S. Bach was born on 21 st March, 1685. J. S. Bach died on 28 th July, 1750.

The parts of a triple

Subject A URI: http://dbpedia.org/resource/Johann_Sebastian_Bach

Predicate

Also a URI:

http://purl.org/dc/terms/creator

Object

Literal or URI:

"Johann Sebastian Bach" http://dbpedia.org/resource/Well-Tempered_Clavier

Plain literals

Essentially strings:

"Johann Sebastian Bach" "The Well-Tempered Clavier"

Plain literals

But can contain language information:

"Johann Sebastian Bach"@en "Бах, Иоганн Себастьян"@ru "The Well-Tempered Clavier"@en "Wohltemperiertes Klavie"@de

Typed literals

And a datatype:

"1685-03-21"^^xsd:date "1750-07-28"^^xsd:date

XML literals "H2O"^^rdf:XMLLiteral

Recap

J. S. Bach composed "The Well Tempered Clavier". J. S. Bach was born on 21 st March, 1685 J. S. Bach died on 28 th July, 1750.

Recap

<http://dbpedia.org/resource/Johann_Sebastian_Bach> dc:creator <http://dbpedia.org/resource/Well-Tempered_Clavier> . <http://dbpedia.org/resource/Well-Tempered_Clavier> dc:title "The Well Tempered Clavier"@en . <http://dbpedia.org/resource/Well-Tempered_Clavier> dc:title "Wohltemperiertes Klavie"@de .

Recap

<http://dbpedia.org/resource/Johann_Sebastian_Bach> p:dateOfBirth "1685-03-21"^^xsd:date .

Recap

<http://dbpedia.org/resource/Johann_Sebastian_Bach> p:dateOfDeath "1750-07-28"^^xsd:date .

Graphs

The Well Tempered Clavier Wohltemperiertes Klavie dc:title dc:title 1685-03-21 1750-07-28 p:dateOfBirth p:dateOfDeath dc:creator

rdf:type

<http://dbpedia.org/resource/Johann_Sebastian_Bach> rdf:type yago:Composer . <http://dbpedia.org/resource/Johann_Sebastian_Bach> rdf:type foaf:Person .

Lists

Performed by Performed by dc:creator Performed by dc:creator rdf:Bag rdf:type

Blank nodes

Representing RDF

RDF/XML <rdf:RDF> <yago:Composer109947232 rdf:about="http://[...]/Johann_Sebastian_Bach" > <p:birthPlace rdf:resource="http://[...]/Eisenach" /> <p:dateOfDeath rdf:datatype="http://[...]/XMLSchema#date" >1750-07-28</p:dateOfDeath> </yago:Composer109947232> </rdf:RDF>

Turtle dbpedia:Johann_Sebastian_Bach p:dateOfBirth "1685-03-21"^^xsd:date; p:dateOfDeath "1750-07-28"^^xsd:date; p:death "1750-07-28"^^xsd:date; p:deathPlace dbpedia:Leipzig; a yago:Composer, foaf:Person .

RDFa

<html>

<head>

<title>

Johann Sebastian Bach

</title>

< link rel ="dc:creator"

href ="http://[...]/Well-Tempered_Clavier" />

<meta property="p:dateOfBirth"

content ="1685-03-21" datatype ="xsd:date" />

</head>

<body>

...

</body>

</html>

RDFa

<html>

<head>

...

</head>

<body>

Johann Sebastian Bach

was born in

<span property="p:dateOfBirth"

content="1685-03-21" datatype="xsd:date"

> 1685 ,

in <span rel="p:placeOfBirth"

resource=" [dbp:Eisenach] "> Eisenach .

</body>

</html>

Storing RDF

Sources of RDF

Querying RDF

SELECT ?composer WHERE { ?composer rdf:type yago:Composer }

<http://dbpedia.org/resource/Johann_Sebastian_Bach>

<http://dbpedia.org/resource/Ludwig_van_Beethoven>

SELECT ?piece WHERE { dbpr: Johann_Sebastian_Bach dc:creator ?piece }

<http://dbpedia.org/resource/Well-Tempered_Clavier>

<http://dbpedia.org/resource/Cello_Suites_%28Bach%29>

Creating vocabularies

Classes

Composer Musician Is a type of Artist Is a type of Creator Is a type of

yago:Composer a rdfs:Class .

yago:Composer rdfs:subClassOf yago:Musician .

yago:Musician rdfs:subClassOf yago:Artist .

yago:Artist rdfs:subClassOf yago:Creator .

yago:Composer rdfs:subClassOf yago:Musician .

yago:Musician rdfs:subClassOf yago:Artist .

yago:Artist rdfs:subClassOf yago:Creator .

dbpedia:Johann_Sebastian_Bach a yago:Composer , foaf:Person .

SELECT ?s WHERE { ?s rdf:type yago:Artist }

Properties

foaf:surname a rdfs:Property .

foaf:surname rdfs:Range rdfs:Literal .

foaf:surname rdfs:Domain foaf:Person .

Validation v. inference

foaf:surname rdfs:Domain foaf:Person .

dbpedia:Johann_Sebastian_Bach foaf:surname "Bach" .

dbpedia:Johann_Sebastian_Bach a foaf:Person .

xyz:composedBy a rdfs:Property .

xyz:composedBy rdfs:Range yago:Composer .

xyz:composedBy rdfs:Domain yago:Piece .

dbp:Cello_Suites_%28Bach%29 xyz:composedBy dbp:Johann_Sebastian_Bach .

dbp:Johann_Sebastian_Bach a yago:Composer .

xyz:composedBy a rdfs:Property .

xyz:composedBy rdfs:Range yago:Composer .

xyz:composedBy rdfs:Domain yago:Piece .

xyz:composedBy rdfs :subPropertyOf dc:creator .

OWL

Conclusion

References

RDF Primer: http://www.w3.org/TR/rdf-primer/

RDF Schema: http://www.w3.org/TR/rdf-schema/

OWL: http://www.w3.org/2004/OWL/

A First Course in RDF and RDFS (Resource Description Framework and Resource Description Framework Schema)

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