Creating Linked Data

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22 Οκτ 2013 (πριν από 4 χρόνια και 17 μέρες)

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Creating Linked Data

Juan F. Sequeda


Semantic Technology Conference

June 2011

Linked Data is a set of best practices
to publish and interlink data

on the web

Linked Data Principles

1.
Use URIs as names for
things

2.
Use HTTP URIs so that
people can look up
(dereference) those
names.

3.
When someone looks up
a URI, provide useful
information.

4.
Include links to other
URIs so that they can
discover more things.

1) Use
URIs

as names for things

1) Use
URIs

as names for things


Uniform Resource Identifiers identify real
world objects and abstract concepts


Not only web documents and digital content


People, places, locations, my car


Know somebody, from somewhere

1) Use
URIs

as names for things

http://
juansequeda.com/foaf.rdf#me

http://www.w3.org/People/Berners
-
Lee/card#i

http://xmlns.com/foaf/0.1/knows

1) Use
URIs

as names for things


http://
juansequeda.com/foaf.rdf#me


Identifies the person


http://
juansequeda.com/foaf.rdf


Identifies an RDF document

2) Use HTTP
URIs

so that people can
look up (dereference) those names.


2) Use HTTP
URIs

so that people can
look up (dereference) those names.



HTTP protocol is the Web’s universal access
mechanism


Linked Data only uses HTTP
URIs


URI: unique name


HTTP URI: universal means of access to the URI


HTTP
URIs

should be
dereferencable

Dereference a URI?

What’s with the redirection?

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>

Minting HTTP
URIs


If you own the domain name and run a web
server at that location, mint
URIs

in this
namespace


I own the domain
mycompany.com


I run a
webserver

http://mycompany.com


I now can mint
URIs

in this namespace:


http://mycompany.com/person/Juan
-
Sequeda


Create Cool
URIs


If you don’t control a namespace, don’t
misuse it


http://www.imdb.com/title


Avoid implementation details


http://foo.mycompany.com:8080/person.php?id=
123&format=rdf


Use Natural Keys within URI


http://mycompany.com/person/Juan
-
Sequeda


http://mycompany.com/person/123


Three different
URIs



URI for the real world object (non
-
information resource)


http://dbpedia.org/resource/London


http://id.mycompany.com/person/Juan
-
Sequeda


http://mycompany.com/person/Juan
-
Sequeda


http://
www.juansequeda.com/foaf.rdf#me


URI for the HTML document (information resource) that describes
the real world object


http://dbpedia.org/page/London


http://
pages.mycompany.com
/person/Juan
-
Sequeda


http://mycompany.com/person/Juan
-
Sequeda.html


URI for the RDF document (information resource) that describes the
real world object


http://dbpedia.org/data/London


http://
data.mycompany.com
/Juan
-
Sequeda


http://mycompany.com/person/Juan
-
Sequeda.rdf


http://
www.juansequeda.com/foaf.rdf

3) Provide useful information

3) Provide useful information


How do we provide useful information in
document form on the web?


HTML


How do we provide useful information in data
form on the web


RDF


Different ways of serializing RDF


RDF/XML


RDFa


N3


turtle

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/resource/
Viva_la_Vida

http:
//
dbpedia.org
/ontology/artist

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#>

http://
dbpedia.org
/resource/Coldplay

http://
dbpedia.org/resource/
Viva_la_Vida

http://
dbpedia.org
/resource
/London

d
bpedia
-
owl:artist

f
oaf:name

d
bprop:origin

g
eo:long

geo:lat

“Coldplay”

51.507778

-
0.128056

<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> .

<?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
>

@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
> .

ntriples

RDF/XML

turtle

HTML

<div>

My name is Bob Smith, but people call me Smithy. Here is my home page:

<a
href
="http://
www.example.com
">
www.example.com
</a>.

I live in Albuquerque, NM and work as an engineer at ACME Corp.

My friends:

<a
href
="
http://darryl
-
blog.example.com
">Darryl</a>,

<a
href
="
http://edna
-
blog.example.com
">Edna</a>

</div>

RDFa

(RDF in HTML)

<div
xmlns:v
="
http://rdf.data
-
vocabulary.org
/#"
typeof
="
v:Person
">


My name is <span property="
v:name
">Bob Smith</span>,


but people call me <span property="
v:nickname
">Smithy</span>.


Here is my homepage:


<a
href
="http://
www.example.com
"
rel
="
v:url
">
www.example.com
</a>.


I live in


<span
rel
="
v:address
">


<span
typeof
="
v:Address
">


<span property="
v:locality
">Albuquerque</span>,


<span property="
v:region
">NM</span>


</span>


</span>


and work as an <span property="
v:title
">engineer</span>


at <span property="
v:affiliation
">ACME Corp</span>.


My friends:


<a
href
="
http://darryl
-
blog.example.com
"
rel
="
v:friend
">Darryl</a>,


<a
href
="
http://edna
-
blog.example.com
"
rel
="
v:friend
">Edna</a>

</div>

What to publish?


Literal Triples

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








<
foaf:name
>











“Coldplay”


Outgoing Links

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








<
owl:sameAs
>











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


Incoming Link

<http://www.bbc.co.uk/music/artists/18690715
-
59fa
-
4e4d
-
bcf3
-
8025cf1c23e0#artist>








<
mo:member_of
>


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

What to publish?


Description of the data set


Semantic Sitemaps


voiD

(Vocabulary of Interlinked Datasets)


Provenance Metadata


Licenses Information

Vocabularies (or Schemas or
Ontologies)


Create your own using


Simple Knowledge Organization Systems (SKOS)


Taxonomy


RDF Vocabulary Description Language (RDF
Schema)


Light weight vocabularies


Web Ontological Language (OWL)


Highly expressive and capable of
inferencing

Vocabularies (or Schemas or
Ontologies)


R
euse vocabularies


Dublin Core: metadata attributes


Friend of a Friend (FOAF): persons and relationships


Semantically Interlinked Online Communities (SIOC):
describing users, posts, blogs, etc


Description of a Project (DOAP)


Music Ontology


Programmes

Ontology: TV and radio programs


Good Relations: describing products and services


Review Vocabulary


Basic Geo (WGS84) Vocabulary

4) Include links to other things

4) Include links to other things


Set external RDF links into other data sources
on the Web


Subject of the triple is in the namespace of one
data set


Object of the triple is a URI in the namespace of
another data set


Connect
siloed

data islands


Enable discovery

4) Include links to other things


Relationship Links

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



<http://xmlns.com/foaf/0.1/based_near>




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


Identity Link

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






<http
://www.w3.org/2002/07/owl
#sameAs>











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


Vocabulary Links

<
http://
purl.org
/ontology/mo
/image
>






<http://www.w3.org/2000/01/rdf
-
schema#subPropertyOf>











<
http://xmlns.com/foaf/0.1/depiction
>






Which predicate for linking to choose?


Depends on your domain


Is it widely used?


owl:sameAs


foaf:knows


foaf:based_near





If you create your own, relate it to a widely
used predicate

How to create the links?


Manually


Works for small and static data sets


I want to find another URI that identifies the same
real object that I have


Sindice

and Falcons provide index of
URIs

by keyword


(Semi) Automatic


Record Linkage/Identity Resolution/Co
-
reference


Silk: http://www4.wiwiss.fu
-
berlin.de/bizer/silk/


LIMES: http://
aksw.org
/Projects/limes