Slides of the Knowledge and Media lecture about Linked Data and Linked Open Data. Presented 19 november 2012. Slides were based on presentations by Victor de Boer and Christophe Guéret

1. LECTURE 7:
LINKED (OPEN) DATA
Marieke van Erp
(with slides from Victor de Boer and Christophe Guéret)

2. TODAY’S LECTURE
• Why Linked (Open) Data?
• What is Linked (Open) Data?
• The story of Linked Open Data
• Contributing to Linked Data
• Standards and best practices
• Consuming Linked Data
• Drawbacks and problems

3. WHY LINKED DATA (1/2)
Slide stolen from Christophe Guéret

4. WHY LINKED DATA (2/2)
Slide stolen from Christophe Guéret

5. ``Sharable, spreadable and nerd-friendly’’
-- Charlotte S H Jensen,

6. WHAT IS LINKED DATA?
• Linked Data is a method to publish
structured data for interlinking with
other data sources
• Standard Web technology (HTTP
and URIs)
• Making information more easily
readable and shareable for machines
• Linked Open Data is a W3C
community project to extend the
Web with open data sets
http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html

7. THE STORY
May 2007

8. Oct

10. “Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/”

11. “Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/”

12. CONTRIBUTING TO LINKED DATA
Yes, it may be scary to open up
your data but it may lead to:
• Transparency
• Participation
• Improvement
• Innovation
• New knowledge & insights
from combined data sources

13. STANDARDS AND BEST
PRACTICES

14. LINKED OPEN DATA FIVE STAR SYSTEM
Available on the web (whatever
★
format), but with an open license
Available as machine-readable
★★ structured data (e.g. excel instead of
image scan of a table)
as (2) plus non-proprietary format (e.g.
★★★
CSV instead of excel)
All the above plus, Use open standards
from W3C (RDF and SPARQL) to
★★★★
identify things, so that people can point
at your stuff
All the above, plus: Link your data to
★★★★★
other people’s data to provide context
www.w3.org/designissues/

15. FOUR RULES OF LINKED DATA
1. Use URIs as names for things (Resources)
2. Use HTTP URIs so that people can look up those names.
(Dereferencing)
3. When someone looks up a URI, provide useful information,
using the standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover more
things.
http://www.w3.org/DesignIssues/

16. FOUR RULES OF LINKED DATA
1. Use URIs as names for things (Resources)
2. Use HTTP URIs so that people can look up those names.
(Dereferencing)
3. When someone looks up a URI, provide useful information,
using the standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover more
things.
http://www.w3.org/DesignIssues/

17. HOW TO MAKE COOL URI’S
• Use HTTP://
• Use a namespace you control
• Unique, stable and persistent
• Don’t use:
• Author name, subject, status, access, file name extension, software mechanism
C://MyDisk/awesome/MvanErp/latest/cgi_bin/rembrandt.html

18. FOUR RULES OF LINKED DATA
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
(Dereferencing)
3. When someone looks up a URI, provide useful information,
using the standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover more
things.
http://www.w3.org/DesignIssues/

19. RDF REMINDER
Subject
Predicate
Object
Triples
am:Rembrandt
am:hasBirthdate
“1651”
am:Rembrandt
foaf:knows
am:PiterLastman
am:PiterLastman
am:wasBornIn
geonames:Amsterdam
ate
am:h asBir thd
“1651” geonames:Amsterdam
am:Rembrandt
foaf:knows
am:w asBorn
In
Graph
am:PiterLastman

20. RDF CONVERSION
<record priref="19319 “ >
<date>1651</date>
<maker>Rembrandt (1606-1669)</maker>
<object.type>etsplaat</object.type>
… priref “19319 ”
</record> date “1651”
am:Record
_:bn1 maker
“Rembrandt (1606-1669)”
object.type “etsplaat”
“19319 ”
iref
:pr
am am:date “1651”
“1234”
am:priref
am:Record am:maker am:Person
am:birthdate
am:proxy-19319 “1606”
am:p-1234
rda:name “Rembrandt”
am
:obje
ct.ty
pe
skos:Concept “etsplaat”
am:etsplaat skos:prefLabel

21. ARCHITECTURE
SPARQL-app Browser
Purl.org
redirect
SPARQL Web interface
HTTP server
Logic
a
RDF(s) storage
tri
pa
clio
Prolog
http://

22. HOW TO ACCESS THE DATA
• PURL 303 redirect to VU semantic layer
http://purl.org/collections/nl/am/proxy-63432
è
http://semanticweb.cs.vu.nl/europeana/browse/list_resource?r=http://
purl.org/collections/nl/am/proxy-63432
• At our server: content negotiation
• HTTP request text/html:
• Local condensed view
• Local full view
• HTTP request application/rdf+xml
• rdf/xml “describe”
• SPARQL endpoint

23. TEXT/HTML

24. TEXT/HTML

25. APPLICATION/RDF+XML
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix ore: <http://www.openarchives.org/ore/terms/> .
@prefix ens: <http://www.europeana.eu/schemas/edm/> .
@prefix ahm: <http://purl.org/collections/nl/am/>
ahm:proxy-66970
a ore:Proxy ;
ahm:title "Zegelstempel Felix Meritis"@nl ;
ahm:material ahm:t-12463 ,
ahm:t-5447 ;
ahm:objectCategory ahm:t-5504 ;
ahm:objectName ahm:t-13817 ,
ahm:t-8489 ;
ahm:objectNumber "KA 7653.1" ;
ahm:priref "66970" .
ahm:proxy-66972
a ore:Proxy ;
ahm:acquisitionDate "0000" ;
ahm:title "Zegelstempel mogelijk van familiewapen"@nl .

26. SPARQL
http://semanticweb.cs.vu.nl/europeana/user/query

27. FOUR RULES OF LINKED DATA
1. Use URIs as names for things
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information,
using the standards (RDF*, SPARQL)
4. Include links to other URIs. so that they can discover more
things.
http://www.w3.org/DesignIssues/

28. LINK TO OTHER SOURCES
“19319 ”
iref
:pr
am am:date “1651”
“1234”
am:priref
am:Record am:maker am:Person
am:birthdate
“1606”
am:proxy-19319 am:p-1234
rda:name “Rembrandt”
owl:sameAs (?)
Viaf:nationality
“Dutch”
Viaf:Person
Viaf:RebrandtvanRijn
“Rembrandt
Harmensz. Van
rdfs:label Rijn”

29. CONSUMING LINKED DATA
• Generic Applications
• Can process any data from any domain
• Domain specific applications
• Covers needs of specific user community

30. LINKED DATA BROWSERS

31. DOMAIN-SPECIFIC APPS

33. DRAWBACKS AND PROBLEMS
• Extra burden on the data provider
• Nerd-only (aka “SPARQL is hard”)
• How do we build user-friendly systems?
• Ranking, user-friendly information presentation
• Scalability (how do you query a huge graph?)
• Licenses
• Is Open always a good idea?
• Context?
• Data quality

34. FURTHER READING
• Tom Heath and Christian Bizer (2011)
Linked Data: Evolving the Web into a
Global Data Space (1st edition).
Synthesis Lectures on the Semantic
Web: Theory and Technology, 1:1,
1-136. Morgan & Claypool (available
online for free)