A SKOS intro

1. SKOS Intro
Jose María Álvarez-Rodríguez
Carlos III University of Madrid
josemaria.alvarez@uc3m.es
1

2. Table of Contents
• SKOS Step by Step
• Appendix
– A real problem to introduce…
• Semantic Web
• RDF
• Linked Data
2

3. SKOS…
• Simple
• Knowledge
• Organization
• System
•
•
•
•
•
•
Thesauri
Controlled vocabularies
Classifications
Taxonomies
Folksonomies
…
• It is a domain-specific Semantic Web vocabulary
• …an OWL ontologyRDF-based model
3

4. Why an organization system?
• Describe:
– Concepts and
– Concept scheme
•
•
•
•
…store
…retrieve
…annotate
…link and merge
– …with existing data
4

5. SKOS entities
Classes or Categories
• Concept
• Concept Scheme
Properties
• Lexical Labels
• Notation
• Documentation
• Semantic relations
• Mapping
Extensions
• SKOS-XL (eXtended Labels)
5

6. PROBLEM STATEMENT
“Whenever the pedal of the brake is
pressed, the car will decelerate
immediately”
6

7. 1-VOCABULARY
“Whenever the pedal of the brake is
pressed, the car will decelerate
immediately”
7

8. A “Car” as a system…
Related-to
Sub-system
Automative Industry
Components of the braking system
8

9. 2-Taxonomy
Car
Braking
…
Subsystem
Pedal
…
…
9

10. Step 1-Modeling Concepts in SKOS
• Create a skos:ConceptScheme
– To collect all skos:Concept in a KOS
• Create a skos:Concept for each entity
10

11. Tip 1-URI design scheme
• Objective:
– Define an URI base
• Concept Scheme and Concepts
• <uri_base>/<project>/<system>/<id>
• How to:
• Slash vs Hash URIS
• ID URIs
– E.g. http://thereusecompany/km/demo/1
• Named URIs
– E.g. http://thereusecompany/km/demo/car
• We will use the prefix km-demo to refer to the URI
http://thereusecompany/km/demo/
11

12. URI Scheme
• URIs for things should be designed to:
–
–
–
–
uniquely name the thing that they name
be in use for a long time
be short and human readable
incorporate existing identifiers where available
• Human-readable URIs?
• Minted URIs? (Am I the owner of the domain?)
– Avoid URIs such as: http://example.org/
http://patterns.dataincubator.org/book/identifier-patterns.html
http://data.gov.uk/resources/uris
12

13. Step 2-Select URIs
km-demo:car
…
km-demo:car/subsystem/braking
…
km-demo:car/subsystem/braking/pedal
13

14. FAQ 1-What happened if the ID contains
more than 1 word or punctuation marks?
• Concept “Pedal of the brake”
– km-demo:car/subsystem/braking/pedal_of_the_brake
• It could be better to use just an ID
– km-demo:car/subsystem/braking/com1
14

15. Step 3-Create skos:Concept
km-demo:car a
skos:Concept .
km-demo:car/subsystem/braking a
skos:Concept .
km-demo:car/subsystem/braking/pedal a
skos:Concept .
15

16. Tip 2-Define our own concepts
• Objective:
– Create our own Categories instead of using
skos:Concept
• How to:
– Define a new category rdfs:subClassOf
skos:Concept
16

17. New categories…
km-demo:System rdfs:subClassOf skos:Concept.
km-demo:car a
km-demo:System.
km-demo:SubSystem rdfs:subClassOf skos:Concept ;
skos:broader km-demo:System.
km-demo:car/subsystem/braking a
km-demo:SubSystem.
km-demo:Component rdfs:subClassOf skos:Concept ;
skos:broader km-demo:SubSystem.
km-demo:car/subsystem/braking/pedal a
km-demo:Component.
17

18. Step 4-Add Authoring properties to
skos:Concept
jose-foaf: http://www.josemalvarez.es/foaf.rdf#.
km-demo:car a km-demo:System ;
dcterms:author jose-foaf:me;
dcterms:created
“2013-10-10"^^xsd:date ;
dcterms:modified
"2013-10-10"^^xsd:date ;.
18

19. Tip 3-Link to existing vocabularies
• Objective:
– Reuse existing data and definitions to enrich concepts.
• How to:
– Try to use widely-accepted vocabularies
•
•
•
•
Dublin-Core Terms (metadata)
Friend Of A Friend (people)
Organizations ontology (organizations)
…
– Avoid the creation of vocabularies from the
scratch
19

20. Step 5-Add Labeling properties to
skos:Concept
km-demo:car a km-demo:System ;
rdfs:label “Car”@en;
skos:prefLabel “Car”@en;
skos:prefLabel “Voiture”@fr;
skos:altLabel “Motor”@en;
skos:altLabel “Bus”@en;
skos:altLabel “Wagon”@fr;
skos:hiddenLabel “Auto-bus”@en;
.
Multilingual Support!
20

21. Tip 4-Use 1 preferred Label
• Objective:
– No two concepts should have the same preferred Label
in a given language.
– Concept descriptor
• How to:
– Use just one skos:prefLabel per concept
– Add more labels through skos:altLabel
and skos:hiddenLabel to specify more
labels
Interoperability enabler
21

22. Tip 5-Use a rdfs:label
• Objective:
– Label all RDF resources
• How to:
– Define a rdfs:label per RDF resource
km-demo:car rdfs:label “Car”@en.
http://patterns.dataincubator.org/book/label-everything.html
22

23. Step 6-Add notation properties to
skos:Concept
km-demo:car a km-demo:System ;
skos:notation "c1"^^xsd:string ;
dcterms:subject "1"^^xsd:string ;
km-demo:level "1";.
23

24. Tip 6-Create my own notation
property
• Objective:
– I want to specialize some notation property
• E.g. Some property to indicate the level in the hierarchy
• How to:
– Define a new property specifying domain and
range
km-demo:level a owl:DatatypeProperty;
rdfs:subClassOf skos:note;
rdfs:label "Level in the hierarchy"@en ;
rdfs:domain skos:Concept;
rdfs:range xsd:int;
.
24

25. Step 7-Add documentation properties
to skos:Concept
km-demo:car a km-demo:System ;
skos:changeNote
"An example of change note."@EN;
skos:editorialNote
"An example of editorial note"@EN;
skos:historyNote
"An example of history note"@EN;
skos:scopeNote
"An example of scope note"@EN;.
Multilingual Support!
25

26. Tip 7-Select hierarchy properties
• Objective:
– I want to define semantic relationships to create an
hierarchy
• How to:
– If non-transitive hierarchy properties are
required…
• skos:broader and skos:narrower
– otherwise...use the transitive version…
• skos:broaderTransitive and
skos:narrowerTransitive
– if symmetric properties are required...
skos:related
26

27. Step 8-Add semantic properties to
skos:Concept
km-demo:car a km-demo:System ;
skos:narrower
km-demo:car/subsystem/braking.
km-demo:car/subsystem/braking a km-demo:SubSystem ;
skos:narrower
km-demo:car/subsystem/braking/pedal.
• skos:broader properties can be inferred by a semantic web
reasoner (be careful)
– broader(x,y)->narrower(y,x)
• Is the relation between “Braking System” and “Pedal” a
broader/narrower one?
maybe part-of…
27

28. Tip 8-Create my own related
property
• Objective:
– I want to specialize some related property
• E.g. Some property to link concepts but asymmetric
• How to:
– Define a new property specifying domain, range
and behavior
km-demo:related-to rdfs:subClassOf skos:semanticRelation;
a owl:AsymmetricObjectProperty;
rdfs:label "Related but asymetric property"@en ;
rdfs:domain skos:Concept;
rdfs:range skos:Concept;
28
.

29. Step 8.1-Using related…
km-demo:Automative a skos:Concept;
…
.
km-demo:car a km-demo:System ;
km-demo:related-to
km-demo:Automative;
.
29

30. Tip 9-Part-of property
• Objective:
– A broader property can be interpreted as a “part-of” relationship
– The first SKOS draft spec. included “broaderPartitative” but it was
finally excluded
• http://www.w3.org/2004/02/skos/extensions/spec/2004-1018.html#broaderPartitive
• How to:
– Keep the semantics of broader relationships
– Define your own property
km-demo:part-of rdfs:subClassOf skos:broader;
a owl:ObjectProperty;
rdfs:label “Part-of relationships"@en ;
rdfs:domain skos:Concept;
rdfs:range skos:Concept;
.
30

31. Step 8.2-Using part-of…
km-demo:car/subsystem/braking/pedal
a km-demo:Component ;
km-demo:part-of
km-demo:car/subsystem/braking;
.
31

32. Step 9-Add mapping properties to
skos:Concept
km-demo2:http://http://thereusecompany/km/demo2/.
dbpedia-res:http://dbpedia.org/resource/
km-demo:car a km-demo:System ;
skos:closeMatch dbpedia-res:Automobile;
skos:exactMatch km-demo2:otherCar;
skos:broadMatch <URI>;
skos:relatedMatch <URI>; .
• Transversal links
• Improve hierarchy browsing
• Be aware of logical implications (in case of
reasoning)
• Try to give a confidence value
• …
32

33. Step 10-Add skos:Concept to a
Concept Scheme
km-demo:car skos:inScheme
<http://thereusecompany/km/demo/ds> .
km-demo:car/subsystem/braking
skos:inScheme
<http://thereusecompany/km/demo/ds> .
km-demo:car/subsystem/braking/pedal
skos:inScheme
<http://thereusecompany/km/demo/ds> .
33

34. Step 11-Describe the concept scheme
<http://thereusecompany/km/demo/1381307095/ds> a
void:Dataset , skos:ConceptScheme ;
rdfs:label "Taxonomy from project Demo"@en ;
dcterms:author <http://www.josemalvarez.es/foaf.rdf#me> ;
dcterms:contributor km-people:JM, km-people:JuanLlorens;
dcterms:description "Demo Vocabulary and Taxonomy" ;
dcterms:license <http://opendatacommons.org/licenses/by/1.0/> ;
dcterms:modified "2013-10-10"^^xsd:date ;
dcterms:publisher km-org:TRC ;
dcterms:source <http://thereusecompany/km/demo/demo.xls> ;
dcterms:title "Demo Vocabulary" ;
void:dataDump
<http://http://thereusecompany/km/demo/1381307095/demo-1381307095.ttl> ;
void:dataDump
<http://http://thereusecompany/km/demo/1381307095/demo-1381307095.rdf> ;
void:exampleResource
<http://thereusecompany/km/demo/1381307095/car>
void:uriRegexPattern
"http://thereusecompany/km/demo/.+" ;
void:vocabulary skos: , dcterms: , rdfs:, km-demo: ;
skos:hasTopConcept <http://http://thereusecompany/km/demo/car>;
foaf:homepage <http://thereusecompany.com> .
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35. A SKOS-based “Car”
km-demo2:http://http://thereusecompany/km/demo2/.
dbpedia-res:http://dbpedia.org/resource/
<http://thereusecompany/km/demo/1381307095/car> a km-demo:System;
dcterms:author jose-foaf:me;
dcterms:created “2013-10-10"^^xsd:date ;
dcterms:modified "2013-10-10"^^xsd:date ;.
rdfs:label “Car”@en;
skos:prefLabel “Car”@en;
skos:prefLabel “Voiture”@fr;
skos:altLabel “Motor”@en;
skos:altLabel “Bus”@en;
skos:altLabel “Wagon”@fr;
skos:hiddenLabel “Auto-bus”@en;
skos:notation "c1"^^xsd:string ;
dcterms:subject "1"^^xsd:string ;
km-demo:level "1";
km-demo:related-to km-demo:Automative;
skos:changeNote "An example of change note."@EN;
skos:editorialNote "An example of editorial note"@EN;
skos:historyNote "An example of history note"@EN;
skos:scopeNote "An example of scope note"@EN;.
skos:narrower km-demo:car/subsystem/braking.
skos:closeMatch dbpedia-res:Automobile;
skos:exactMatch km-demo2:otherCar;
skos:inScheme <http://thereusecompany/km/demo/1381307095/ds>.
35

36. A SKOS-based “Braking” system
km-demo:car/subsystem/braking a km-demo:SubSystem ;
…
skos:inScheme <http://thereusecompany/km/demo/ds> .
km-demo:car/subsystem/braking/pedal a km-demo:Component ;
…
km-demo:part-of km-demo:car/subsystem/braking;
skos:inScheme <http://thereusecompany/km/demo/ds> .
36

37. SKOS Concept Template
<base_uri>/km/<project>/<timestamp>/<concept_id>
<concept_id> :: c[0-9]+
a skos:Concept ;
#----------1-Authoring properties dcterms:*---------------------dcterms:author <URI>;
dcterms:created "2013-10-10"^^xsd:date ;
dcterms:modified "2013-10-10"^^xsd:date ;
#----------2-Lexical labels---------------------rdfs:label "Foo label"@LANG;
skos:prefLabel "Foo preferred label"@LANG;
skos:altLabel ”Foo alternative label"@LANG;
#----------3-Documentation properties
skos:changeNote "Change note"@LANG;
skos:editorialNote "Editorial note"@LANG;
skos:historyNote "History note"@LANG;
skos:scopeNote "Scope note"@LANG;
#----------4-Notation properties
skos:notation "id"^^xsd:string ;
dcterms:subject "id, subject,..."^^xsd:string ;
km:level "1";
#----------5-Semantic and hierarchy properties
#
if symmetric properties are required...
skos:related <URI>;
#
otherwise
km:related <URI>;
#
if non-transitive hierarchy properties are required...Moreover we could only serialize one of them, the other can be inferred:
skos:narrower <URI>;
skos:broader <URI>;
#
otherwise...use the transitive version...that can also be inferred.
skos:narrowerTransitive <URI>;
skos:broaderTransitive <URI>;
#----------6-Mapping properties
skos:closeMatch|exactMatch... <URI>;
#----------7-Concept Scheme
skos:inScheme <URI> ;
.
37

38. SKOS Benefits
• A concept-oriented model
• RDF-based
– a common and shared data model
•
•
•
•
•
•
•
Crucial contribution to interoperability
A way of porting KOS to RDF
Align to existing standards (ISO 25964)
Lightweight reasoning
Simple but powerful
Extensible
…
38

39. SKOS is being used…
• Most of the semantic web-based vocabularies
– E.g. The RDF Data Cube Vocabulary
• Porting the SDMX standard for statistics to RDF
• Most of the semantic web-based vocabularies
• To Boost the Linked Data initiative…
What’s next…
• SKOS-XL (eXtensions for Labels)
• W3C Provenance and Trust
39

40. References
• http://www.w3.org/TR/skos-reference/
• http://www.iskouk.org/presentations/isaac_2107200
8.pdf
• http://www.w3.org/2004/02/skos/references
40