1. Linked Data and RDF
Semantic Engineering Seminar WS 2013/14
Daniel Nüst
daniel.nuest@wwu.de

2. Linked Data
WWW > Web of Documents
CSV, XML, HTML tables >>> Web of Data
Typed Links, to & from >>> global data graph
LOD

3. Principles
1. Use URIs to denote things.
2. Use HTTP URIs [#, /] so that these things can be
referred to and looked up ("dereferenced") by
people and user agents.
3. Provide useful information [metadata (aliases,
DC terms, technical: means of access, formats)]
about the thing when its URI is dereferenced,
leveraging standards such as RDF, SPARQL.
4. Include links to other [!] related things (using
their URIs) when publishing data on the Web
[reusing vocabularies].
http://en.wikipedia.org/wiki/Linked_data

4. 2.46 billion pieces of information (RDF triples)
http://lod-cloud.net/ http://dbpedia.org/

5. http://lov.okfn.org/dataset/lov/index.html

6. http://lov.okfn.org/dataset/lov/details/vocabulary_geo.html

7. RDF (.rdf)
“HTML for data”
the thing
the value
the property
Goals/Applications
transfer information between machines (not people) without loss of meaning,
“identified on the web”
Vocabularies (terms) for statements
Serializations
http://www.w3.org/TR/rdf-primer/
<Subject> <Predicate> <Object>

8. http://www.w3.org/TR/rdf-primer/
http://www.example.org/index.html has a creator whose value is John Smith

9. http://www.example.org/index.html has a creator whose value is John Smith
http://www.w3.org/TR/rdf-primer/
http://www.example.org/index.html has a creation-date whose value is August 16, 1999
http://www.example.org/index.html has a language whose value is English

10. <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> <http://www.example.org/staffid/8574
<http://www.example.org/index.html> <http://www.example.org/terms/creation-date> "August 16, 1999" .
<http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/language> "en" .
(shared) Vocabularies
namespace URI: http://www.example.org/
convention
ex:index.html dc:creator exstaff:85740 .
ex:index.html exterms:creation-date "August 16, 1999" .
ex:index.html dc:language "en" .
fy:joefy.iunm ed:dsfbups fytubgg:85740 .
http://www.w3.org/TR/rdf-primer/
prefix ex:
prefix dc:
namespace URI: http://purl.org/dc/elements/1.1/
prefix exterms: namespace URI: http://www.example.org/terms/
prefix exstaff: namespace URI: http://www.example.org/staffid/

11. John Smith has a an age whose value is 27
<http://www.example.org/staffid/85740> <http://www.example.org/terms/age>
"27"^^<http://www.w3.org/2001/XMLSchema#integer> .
ex:index.html exterms:creation-date "1999-08-16"^^xsd:date .
http://www.w3.org/TR/rdf-primer/
exstaff:85740 exterms:age "27"^^xsd:integer .

12. Concepts Things you should have heard about …
Data types
Expression of simple facts
Entailment
[Literals, URIrefs, RDF/XML, graphs]
http://www.w3.org/TR/rdf-concepts
Blank nodes

13. http://www.w3.org/TR/rdf-primer/

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

15. Turtle (.ttl)
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.
@prefix contact: <http://www.w3.org/2000/10/swap/pim/contact#>.
<http://www.w3.org/People/EM/contact#me>
rdf:type contact:Person;
contact:fullName "Eric Miller";
contact:mailbox <mailto:em@w3.org>;
contact:personalTitle "Dr.".
http://www.w3.org/2007/02/turtle/primer/

16. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdfsyntax-ns#"
xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#">
<geo:Point>
<geo:lat>55.701</geo:lat>
<geo:long>12.552</geo:long>
</geo:Point>
</rdf:RDF>
http://www.w3.org/2003/01/geo/#example
Geo and RDF

17. <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns="http://xmlns.com/foaf/0.1/">
<Person>
<name>Dan Brickley</name>
<homepage dc:title="Dan's home page"
rdf:resource="http://danbri.org/"/>
<based_near geo:lat="51.47026" geo:long="2.59466"/>
<rdfs:seeAlso rdf:resource="http:/danbri.org/foaf.rdf"/>
<!-- more RDF here, using any RDF vocabularies -->
</Person>
</rdf:RDF>
http://www.w3.org/2003/01/geo/#example
Geo, FOAF & DC

18. Resources and references > see handout!
THANKS!

20. Linked data applications
browsers – navigate/traverse data sources using
links/RDF triples (connecting web of {documents, data})
search engines – start of the navigation
human-oriented (like Google…)
application-oriented (reuse indexing for different apps)
domain applications
Dbpedia Mobile, Revyu, DERI pipes, …

21. RDFa 1.0 Example
http://en.wikipedia.org/wiki/RDFa

22. RDFs and OWL
RDF Schema > http://en.wikipedia.org/wiki/RDF_Schema
Web Ontology Language > http://en.wikipedia.org/wiki/Web_Ontology_Language
more expressive
See also https://www.cambridgesemantics.com/de/semantic-university/rdfs-vs.-owl