Consuming linked data by machines

Consuming Linked Data
by Machines
Consuming Linked Data Tutorial
ISWC 2009, Washington DC
Patrick Sinclair, BBC

RDF

Resource Description Framework

Juan introduced RDF earlier, and it’s one of the key elements to Linked Data as it’s how data is
expressed on the web: when you want to fetch some information about a resource, it is returned in
RDF.

RDF
subject - predicate - object
Coldplay is the artist of Viva la Vida

Coldplay is the artist of Viva la Vida

http://dbpedia.org/resource/Coldplay

http://dbpedia.org/ontology/artist

http://dbpedia.org/resource/Viva_la_Vida
With RDF, you make statements about resources using subject-predicate-object expressions.

* For example, if you want to say that “Coldplay is the artist of the album Viva la Vida”.

* The subject is “Coldplay”, the predicate is “is the artist of”, and the “object” is “Viva la vida”.

And in RDF we’re using URIs.
* So there’s a URI for Coldplay

And a URI for Viva la vida.

And here is the URI for the property indicating the artist for an album.

prefix dbpedia-owl: <http://dbpedia.org/ontology/>
prefix foaf: <http://xmlns.com/foaf/0.1/>
prefix dbprop: <http://dbpedia.org/property/>
prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>

51.507778 -0.128056

geo:lat geo:long

http://dbpedia.org/resource/London

dbprop:origin


dbpedia-owl:artist foaf:name
“Coldplay”
http://dbpedia.org/resource/Viva_la_Vida
And using these triple expressions, you build up a graph of data...

<http://dbpedia.org/resource/Coldplay> <http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .
<http://dbpedia.org/resource/Coldplay> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Band> .

ntriples

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<dbpedia-owl:Band xmlns:dbpedia-owl="http://dbpedia.org/ontology/"
rdf:about="http://dbpedia.org/resource/Coldplay">
<dbpedia-owl:artist rdf:resource="http://dbpedia.org/resource/Viva_la_Vida"/>
</dbpedia-owl:Band>
</rdf:RDF>

RDF/XML

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

<http://dbpedia.org/resource/Coldplay>
a <http://dbpedia.org/ontology/Band> ;
<http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .

turtle
Coming back to RDF, it’s important to note that RDF is a model, a way to describe data - and there
are different serialisations of RDF.

Here are 2 triples expressed in the ntriples format: it’s the most basic format.
You simply get subject - predicate - object - new line, subject - predicate - object - new line

Here is the most established RDF format: RDF/XML - unfortunately this is the format most people
are exposed to when learning about RDF.
It’s horrible to read, it’s ugly - it’s just not user friendly at all!

Luckily, there’s turtle: it let’s you write RDF graphs in a compact text format.
In turtle, you can see what those 2 triples are saying:
The resource here Coldplay, has a type Band, and it’s the artist for this other resource Viva la vida.

Web of Documents Web of Data

So RDF and the Web of Data - how does it relate to the web of documents that everyone is familiar
with?

http://www.ﬂickr.com/photos/danbri/2415237566/
Actually it’s all the same thing: it’s just the web!

There are web documents to be consumed by humans, and there are RDF documents to be
consumed by machines, and they live on the web. And these documents describe real objects:
people, houses, relationships...

And you link from the web documents to the RDF documents...

http://www.w3.org/Talks/WWW94Tim/

Content Negotiation

A big part of how this all works is content negotiation: when you make an http request you can
specify what format you’d prefer the response back, and the server will do it’s best to return stuff in
the format you speciﬁed it.

So you can say: I’d like this resource about Yves...

And if you want RDF, you can ask for

http://dbpedia.org

I want to show you what happens when you fetch RDF
But ﬁrst I want to introduce DBpedia, as the examples I’ve been showing uses DBpedia URIs.

{{Infobox musical artist
| Name = Coldplay
| Img = Coldplay - December 2008.jpg
| Img_capt = Coldplay, from left to right: {{nowrap|
[[Guy Berryman]],}} {{nowrap|[[Jonny Buckland]],}} {{nowrap|
[[Chris Martin]],}} and {{nowrap|[[Will Champion]]}}
| Img_size = 250
| Landscape = yes
| Background = group_or_band
| Origin = London, England
| Genre = [[Alternative rock]]
| Years_active = 1998–present
| Label = [[Parlophone Records|
Parlophone]]<br>[[Capitol Records|Capitol]]<br>[[Fierce Panda
Records|Fierce Panda]]
| URL = [http://www.coldplay.com/ coldplay.com]
| Current_members = [[Chris Martin]]<br />[[Jonny
Buckland]]<br />[[Guy Berryman]]<br />[[Will Champion]]
}}

http://en.wikipedia.org/wiki/Coldplay
The DBpedia project is extracting structured data from Wikipedia, and making it available as Linked
Data.

It’s mostly based on extracting data from InfoBoxes on the Wikipedia articles.

And it uses the Wikipedia article title in the URI for the RDF resource.

curl --include --location --header "Accept: text/html" http://dbpedia.org/resource/Coldplay

HTTP/1.1 303 See Other
Server: Virtuoso/06.00.3123 (Solaris) x86_64-sun-solaris2.10-64 VDB
Connection: close
Content-Type: text/html; charset=ISO-8859-1
Date: Fri, 23 Oct 2009 14:01:26 GMT
Accept-Ranges: bytes
Location: http://dbpedia.org/page/Coldplay
Content-Length: 0

HTTP/1.1 200 OK
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8
Date: Fri, 23 Oct 2009 14:01:26 GMT
Expires: Sat, 24 Oct 2009 14:01:26 GMT
Link: <http://dbpedia.org/data/Coldplay.rdf>;
rel="alternate"; title="Metadata in RDF/XML format",
<http://dbpedia.org/data/Coldplay.n3>;
rel="alternate"; title="Metadata in N3/Turtle format",
<http://dbpedia.org/data/Coldplay.json>;
rel="alternate"; title="Metadata in JSON+RDF format"
Content-Length: 87951

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-
rdfa-1.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:dbpprop="http://dbpedia.org/property/"
xmlns:owl="http://www.w3.org/2002/07/owl#"
version="XHTML+RDFa 1.0" xml:lang="en">


<head profile="http://www.w3.org/1999/xhtml/vocab">
<title>About: Coldplay</title>

curl --include --location --header "Accept: application/rdf+xml" http://dbpedia.org/resource/Coldplay

Connection: close
Date: Fri, 23 Oct 2009 15:02:52 GMT
TCN: choice
Vary: negotiate,accept
Content-Location: Coldplay.xml
Content-Type: application/rdf+xml; qs=0.95
Location: http://dbpedia.org/data/Coldplay.xml
Content-Length: 0

HTTP/1.1 200 OK
Date: Fri, 23 Oct 2009 15:02:52 GMT
X-SPARQL-default-graph: http%3A%2F%2Fdbpedia.org
Content-Type: application/rdf+xml; charset=UTF-8

<?xml version="1.0" encoding="utf-8" ?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/
2000/01/rdf-schema#">
<rdf:Description rdf:about="http://dbpedia.org/resource/Coldplay"><rdfs:label
xml:lang="pt">Coldplay</rdfs:label></rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Coldplay"><skos:subject xmlns:skos="http://
www.w3.org/2004/02/skos/core#" rdf:resource="http://dbpedia.org/resource/
Category:English_musical_groups"/></rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Sparks_%28EP%29"><dbpprop:artist
xmlns:dbpprop="http://dbpedia.org/property/" rdf:resource="http://dbpedia.org/resource/Coldplay"/></
rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/God_Put_a_Smile_upon_Your_Face"><dbpedia-
owl:artist xmlns:dbpedia-owl="http://dbpedia.org/ontology/" rdf:resource="http://dbpedia.org/
resource/Coldplay"/></rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Viva_la_Vida"><dbpedia-owl:band
xmlns:dbpedia-owl="http://dbpedia.org/ontology/" rdf:resource="http://dbpedia.org/resource/Coldplay"/
></rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Coldplay"><rdfs:comment xml:lang="it">I
Coldplay sono un gruppo alternative rock britannico. Hanno venduto 50 milioni di dischi in tutto il
mondo.</rdfs:comment></rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Lost%21"><dbpedia-owl:band xmlns:dbpedia-
owl="http://dbpedia.org/ontology/" rdf:resource="http://dbpedia.org/resource/Coldplay"/></
rdf:Description>
<rdf:Description rdf:about="http://dbpedia.org/resource/Coldplay"><dbpprop:commonsCatProperty
xmlns:dbpprop="http://dbpedia.org/property/" xml:lang="en">Coldplay</dbpprop:commonsCatProperty></

curl --include --location --header "Accept: text/rdf+n3" http://dbpedia.org/resource/Coldplay

Connection: close
Date: Fri, 23 Oct 2009 15:05:56 GMT
TCN: choice
Vary: negotiate,accept
Content-Location: Coldplay.n3
Content-Type: text/rdf+n3; qs=0.8
Location: http://dbpedia.org/data/Coldplay.n3
Content-Length: 0

HTTP/1.1 200 OK
Date: Fri, 23 Oct 2009 15:05:57 GMT
X-SPARQL-default-graph: http%3A%2F%2Fdbpedia.org
Content-Type: text/rdf+n3; charset=UTF-8

@prefix dbpprop:   <http://dbpedia.org/property/> .
@prefix dbpedia:   <http://dbpedia.org/resource/> .
<http://dbpedia.org/resource/22_Dreams>   dbpprop:after   dbpedia:Coldplay .
@prefix dbpedia-owl:   <http://dbpedia.org/ontology/> .
dbpedia:Parachutes   dbpedia-owl:artist   dbpedia:Coldplay ;
   dbpprop:artist   dbpedia:Coldplay .
dbpedia:God_Put_a_Smile_upon_Your_Face   dbpedia-owl:band   dbpedia:Coldplay ;
   dbpedia-owl:artist   dbpedia:Coldplay ;
dbpedia:Live_2003   dbpedia-owl:artist   dbpedia:Coldplay ;
<http://dbpedia.org/resource/Safety_%28EP%29>   dbpedia-owl:artist   dbpedia:Coldplay ;

What’s with the
redirection?

http://en.wikipedia.org/wiki/File:MagrittePipe.jpg

I think the best way to describe this is using this painting by René Magritte, which shows a pipe but
written below is "Ceci n'est pas une pipe" (This is not a pipe).

The painting is not a pipe, but rather an image of a pipe.
Magritte himself said that of course it was not a pipe, just try to ﬁll it with tobacco.

<http://upload.wikimedia.org/.../coldplay.jpg>

Ceci n’est pas Coldplay
http://upload.wikimedia.org/wikipedia/commons/e/e1/Coldplay_-_December_2008.jpg

So if we extend this to our Coldplay example, this photo is not Coldplay!

About: Coldplay
An Entity in Data Space: dbpedia.org

'Coldplayare a British alternative rock band formed in London, England in 1998.

Property Value
dbpedia-owl:background group_or_band
dbpedia-owl:currentMembers dbpedia:Chris_Martin
dbpedia:Jonny_Buckland
dbpedia:Will_Champion
dbpedia:Guy_Berryman
dbpedia-owl:genre dbpedia:Alternative_rock
dbpedia-owl:label dbpedia:EMI
dbpedia:Parlophone_Records
dbpedia:Capitol_Records
dbpprop:abstract 'Coldplayare a British alternative rock band formed in London, England in 1998. The group comprises vocalist/pian
Chris Martin, lead guitarist Jonny Buckland, bassist Guy Berryman, and drummer/backing vocalist/multi-instrumenta
Champion. Coldplay has sold 50 million albums, and are also known for their hit singles, such as "Yellow", "The Sc
"Clocks", "Speed of Sound", "Fix You" and "Viva la Vida". Coldplay achieved worldwide fame with the release of th
"Yellow", followed by their debut album, Parachutes (2000), which was nominated for the Mercury Prize. Its follow-
Blood to the Head, won multiple awards such as NMEs Album of the Year. Their next release, X&Y, received a slig
enthusiastic yet still generally positive reception. The band's fourth studio album, Viva la Vida or Death and All His
produced by Brian Eno and released again to largely favourable reviews, earning several Grammy nominations and
Coldplay's albums have enjoyed commercial success. Coldplay's early material was compared to acts such as Rad
Buckley, U2, and Travis. Since the release of Parachutes, Coldplay have drawn influence from other sources, inclu
the Bunnymen, Kate Bush and George Harrison on A Rush of Blood to the Head, Johnny Cash and Kraftwerk for X
Arcade Fire and My Bloody Valentine on Viva la Vida. Coldplay have been an active supporter of various social an
causes, such as Oxfam's Make Trade Fair campaign and Amnesty International. The group have also performed a
projects such as Band Aid 20, Live 8, Sound Relief, and the Teenage Cancer Trust.
Coldplay er et engelsk band, der i genre svinger imellem pop og let/alternativ rock. Coldplay er af mange udråbt so
vigtigste bands i slutningen af 1990'erne og starten af det nye årtusinde, og nogle sammenligner endda deres statu
Radiohead og U2. Bandet består af:*Chris Martin: Forsanger, piano, keyboard, guitar *Jon Buckland: Guitar, harmo
*Guy Berryman: Bas, synthesizer, harmonika, sang *Will Champion: Trommer/percussion, piano, sangColdplay har
været i Danmark. Blandt andet var de et af hovednavnene på Roskilde Festivalen i 2003, i forbindelse med udgive
dato, nok mest anerkendte album A Rush of Blood to The Head. Senest de har lagt vejen forbi København var i 20

<http://dbpedia.org/page/Coldplay>

Ceci n’est pas Coldplay
And this web page from DBpedia is not Coldplay, it’s a web page describing Coldplay!

"2009-05-18T22:36:41+01:00"
About: Coldplay


dcterms:created
Property Value
dbpprop:abstract 'Coldplayare a British alternative rock band formed in London, England in 1998. The group comprises vocalist/pianist/guitarist
Chris Martin, lead guitarist Jonny Buckland, bassist Guy Berryman, and drummer/backing vocalist/multi-instrumentalist Will
Champion. Coldplay has sold 50 million albums, and are also known for their hit singles, such as "Yellow", "The Scientist",
"Clocks", "Speed of Sound", "Fix You" and "Viva la Vida". Coldplay achieved worldwide fame with the release of their single
"Yellow", followed by their debut album, Parachutes (2000), which was nominated for the Mercury Prize. Its follow-up, A Rush of
Blood to the Head, won multiple awards such as NMEs Album of the Year. Their next release, X&Y, received a slightly less
enthusiastic yet still generally positive reception. The band's fourth studio album, Viva la Vida or Death and All His Friends, was
produced by Brian Eno and released again to largely favourable reviews, earning several Grammy nominations and wins. All of
Coldplay's albums have enjoyed commercial success. Coldplay's early material was compared to acts such as Radiohead, Jeff
Buckley, U2, and Travis. Since the release of Parachutes, Coldplay have drawn influence from other sources, including Echo and
the Bunnymen, Kate Bush and George Harrison on A Rush of Blood to the Head, Johnny Cash and Kraftwerk for X&Y and Blur,
Arcade Fire and My Bloody Valentine on Viva la Vida. Coldplay have been an active supporter of various social and political
causes, such as Oxfam's Make Trade Fair campaign and Amnesty International. The group have also performed at various charity
Coldplay er et engelsk band, der i genre svinger imellem pop og let/alternativ rock. Coldplay er af mange udråbt som et af de
vigtigste bands i slutningen af 1990'erne og starten af det nye årtusinde, og nogle sammenligner endda deres status med både
Radiohead og U2. Bandet består af:*Chris Martin: Forsanger, piano, keyboard, guitar *Jon Buckland: Guitar, harmonika, sang
*Guy Berryman: Bas, synthesizer, harmonika, sang *Will Champion: Trommer/percussion, piano, sangColdplay har flere gange
været i Danmark. Blandt andet var de et af hovednavnene på Roskilde Festivalen i 2003, i forbindelse med udgivelsen af deres til
dato, nok mest anerkendte album A Rush of Blood to The Head. Senest de har lagt vejen forbi København var i 2005 på deres

<http://dbpedia.org/page/Coldplay>

<http://upload.wikimedia.org/.../coldplay.jpg>
foaf:primaryTopic
dcterms:created
foaf:depiction
"2007-05-18T19:31:51+01:00"

dbpedia-owl:formed
"1998"

And it’s important to make this distinction, because it allows us to make different claims about the
thing and the documents describing the thing

So we want to talk about when Coldplay the band was formed.
And for the webpage and the image, we want to say when they were created.

And we can link these things together.
The page’s primary topic is Coldplay, and the image depicts the Band.

Information Resource Non-Information Resource
About: Coldplay


Property Value

http://dbpedia.org/page/Coldplay http://dbpedia.org/resource/Coldplay

http://upload.wikimedia.org/.../coldplay.jpg

So there’s a distinction between Information Resources (web documents, images, RDF data) and
Non-Information resources, which are the things you can’t send down a wire (people, places,
things).

System dereferencing
in text/html

HTTP GET request (text/html)
HTTP 303 response http://dbpedia.org/resource/Coldplay
http://dbpedia.org/page/Coldplay

time
HTTP GET request
http://dbpedia.org/page/Coldplay About: Coldplay


Property Value

HTTP 200 response

HTML data

in application/rdf+xml

HTTP GET request (application/rdf+xml)
HTTP 303 response http://dbpedia.org/resource/Coldplay
http://dbpedia.org/data/Coldplay.xml

time
HTTP GET request
http://dbpedia.org/data/Coldplay.xml
<rdf/>
HTTP 200 response describing
RDF data Coldlay

http://www.bbc.co.uk/music/artists/:id
http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234

Text only Help Search Explore the BBC

QUICK FIND Enter an artist name ...

BBC Music Artists Coldplay

Coldplay
Group. Formed September 1996.

Played By
Since December 2008

1.

Greg James
BBC Radio 1

2.

Edith Bowman
BBC Radio 1

3.
Latest News Stories
NEWS FROM THE BBC Chris Hawkins
BBC 6 Music
Simon Pegg plays with Coldplay
Sat 19 Sep 2009 15:24 Actor Simon Pegg joins Coldplay on stage at Wembley Stadium on
Friday night at the...
4.
No change for Girls' Coldplay set
Thu 17 Sep 2009 14:10 Girls Aloud say they will not make any concessions to rock fans when
they support...
Scott Mills
Coldplay copyright case 'settled' BBC Radio 1
Wed 16 Sep 2009 13:27 Coldplay and Joe Satriani reach agreement over a court case alleging

http://www.bbc.co.uk/music/artists/:id.rdf
http://www.bbc.co.uk/music/artists/:id#artist
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix mo: <http://purl.org/ontology/mo/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-
d52ba2e14234.rdf>
rdfs:label "Description of the artist Coldplay" ;
foaf:primaryTopic <http://www.bbc.co.uk/music/artists/cc197bad-
dc9c-440d-a5b5-d52ba2e14234#artist> .

<http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-
d52ba2e14234#artist>
a mo:MusicArtist, mo:MusicGroup ;
foaf:name "Coldplay" ;
owl:sameAs <http://dbpedia.org/resource/Coldplay> ;
foaf:page <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-
a5b5-d52ba2e14234.html> .
We can also use Hash URIs to refer to non-information resource.

in text/html

HTTP GET request (text/html)
<html/>
time HTTP 200 response describing
HTML Data Coldplay

in application/rdf+xml

HTTP GET request (application/rdf+xml)
<rdf/>
RDF Data Coldplay

RDFa

<html>
...
<div xmlns:dc="http://purl.org/dc/elements/1.1/">
<h2 property="dc:title">The trouble with Bob</h2>
<h3 property="dc:creator">Alice</h3>
...
</div>
...
</html>

A further option is to use RDFa, where RDF is embedded into the HTML markup directly.

in RDFa

HTTP GET request
http://www.bbc.co.uk/music/artists/:id
<html+rdf>
HTML + RDF Data Coldplay

Let’s consume some RDF!

rapper

Rapper is a tool for parsing RDF data and outputting in different formats.

rapper http://dbpedia.org/resource/Coldplay

=> returns triples

e.g.
<http://dbpedia.org/ontology/artist>
<http://dbpedia.org/resource/Viva_la_Vida> .

So when we run rapper on a Linked Data URI we get back triples, e.g.

<http://dbpedia.org/resource/Coldplay> <http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .

rapper -oturtle http://dbpedia.org/ontology/artist

=> returns data formatted in turtle

@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

a owl:ObjectProperty ;
rdfs:label "artist" .

And if everything is linked data, then we can go and dereference the property and ﬁnd out more
about it: e.g. there’s a human readable label for this property you can use in your application.


a <http://dbpedia.org/ontology/Band> ;
<http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .

<http://dbpedia.org/ontology/Band>


And coming back to the data about an artist, you can see how there are these special URIs that are
let you describe what the resource is.

* So there is this URI that says Coldplay is a band
* And this URI is the property we saw earlier, it says an artist created a record.

You can deﬁne vocabularies and ontologies that allow you to describe a speciﬁc domain.

Vocabularies and Ontologies

• people
• social media
• commerce
• events
• radio and tv programmes
• music
• etc
And there are plenty of vocabularies available out there that can be used.

owl:sameAs
http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist

=

=
http://dbtune.org/musicbrainz/resource/artist/cc197bad-dc9c-440d-a5b5-d52ba2e14234

=
http://dbtune.org/myspace/coldplay

=
http://lastfm.rdﬁze.com/artists/Coldplay
Just want to quickly mention one property of the Web Ontology Language that comes up a lot in
Linked Data discussions: the owl:sameAs property.

It allows us to declare that non-information resources across the web are the same thing

So the BBC's Coldplay is the same as...

•
...the DBpedia Coldplay is the same as...

•
...the MusicBrainz Coldplay is the same as...

•
...the Myspace Coldplay is the same as...

•
...the last.fm New Order is the same as...

•
...etc

And this makes it possible to aggregate data about a particular thing from different sources really
easily.

Consuming BBC Linked
Data using Tabulator

http://moustaki.org/resources/screencast-music.ogv

Consuming linked data by machines

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