"Classification schemes, thesauri and other Knowledge Organization Systems - a Linked Data perspective". Presentation at the Pelagios Linked Pasts event, July 20-21, 2015. http://pelagios-project.blogspot.co.uk/2015/03/linked-pasts.html

1. Classification schemes, thesauri and other
Knowledge Organization Systems
- a Linked Data perspective
Antoine Isaac
Pelagios: Linked Pasts
London, July 20-21, 2015

2. Classification schemes?
Scope: knowledge organization systems (KOS) such as
classification systems, thesauri, gazetteers, subject
heading lists…
(last-minute addition: also time periods, cf. PeriodO  )

6. Simple Knowledge Organization System
SKOS is for exchanging KOSs as Linked Data (in RDF)
• Better than semi-structured data (CSV)
• Still relatively simple

7. A SKOS graph
animals
cats
UF domestic cats
RT wildcats
BT animals
SN used only for domestic cats
domestic cats
USE cats
wildcats

8. Representing semantics
The formal way: OWL Semantic Web ontology language
Used for ontologies that enable machine reasoning
Mother is a class
Parent is the class of entities of type Person that are related to
at least one other resource of type Person using the child
property
…

9. Do we want to represent every vocabulary
as a formal ontology?
It is possible, but not easy
 KOS are large
 KOS have softer “semantics”
Parent RelatedTerm Child
 KOS have a focus on terminological information
Child UsedFor Offspring
Softer semantics can be useful for many applications!

10. Europeana and knowledge organisation systems
 Create a “semantic layer” on top of cultural heritage objects
From: Stefan Gradmann

11. Using KOS in the Europeana Data Model

12. Enhanced descriptive metadata

13. Using KOS Linked Data
<skos:Concept rdf:about="http://www.mimo-db.eu/InstrumentsKeywords/2251">
<skos:prefLabel xml:lang="">Harpsichord</skos:prefLabel>
<skos:prefLabel xml:lang="de">Cembalo</skos:prefLabel>
<skos:prefLabel xml:lang="sv">Cembalo</skos:prefLabel>
<skos:prefLabel xml:lang="fr">Clavecin</skos:prefLabel>
<skos:prefLabel xml:lang="it">Clavicembalo</skos:prefLabel>
<skos:prefLabel xml:lang="en">Harpsichord</skos:prefLabel>
<skos:prefLabel xml:lang="nl">Klavecimbel</skos:prefLabel>
<skos:broader>
<skos:Concept rdf:about="http://www.mimo-db.eu/InstrumentsKeywords/2239">
<skos:prefLabel>Harpsichords</skos:prefLabel>
</skos:Concept>
</skos:broader>
</skos:Concept>

14. Other types of contextual resources
<gn:Feature rdf:about="http://sws.geonames.org/3176959/">
<gn:name>Florence</gn:name>
<gn:alternateName xml:lang="ko"> 피렌체 </gn:alternateName>
<gn:alternateName xml:lang="ja"> フィレンツェ </gn:alternateName>
<gn:alternateName xml:lang="th">ฟลอเรนซ์</gn:alternateName>
<gn:alternateName xml:lang="bo">ཧྥུ་ལོ་རོན་ཟིའུ་ཡ།</gn:alternateName>
<gn:alternateName xml:lang="cy">Fflorens</gn:alternateName>
<gn:alternateName xml:lang="bs">Firenca</gn:alternateName>
<gn:alternateName xml:lang="hbs">Firenca</gn:alternateName>
<gn:alternateName xml:lang="hr">Firenca</gn:alternateName>
<gn:alternateName xml:lang="sq">Firenca</gn:alternateName>
<gn:alternateName xml:lang="pl">Firence</gn:alternateName>
<gn:alternateName xml:lang="sl">Firence</gn:alternateName>
<gn:alternateName xml:lang="lij">Firense</gn:alternateName>
<gn:population>371517</gn:population>
<wgs84_pos:lat>43.76667</wgs84_pos:lat>
<wgs84_pos:long>11.25</wgs84_pos:long>

15. http://blogs.getty.edu/iris/art-
architecture-thesaurus-now-
available-as-linked-open-data/

16. Multilingual search
'uurglazen' in Italy
http://europeana.eu/portal/search.html?
query=uurglazen&rows=96&qf=COUNTRY%3Aitaly

19. Vocabularies currently provided to Europeana

20. Europeana metadata enrichment

21. Enrichment types and vocabularies
Enrichment
Type
Target
vocabulary
Source metadata
fields
Number of
enriched
objects
Places GeoNames dcterms:spatial,
dc:coverage
7M
Concepts GEMET,
DBpedia,
dc:subject,
dc:type
9.2M
Agents DBpedia dc:creator,
dc:contributor
144K
Time Semium Time dc:date,
dc:coverage,
dcterms:temporal,
edm:year
10,2M

22. Work in progress
Entity-based search and browsing
Annotation
Pundit @ DM2E project http://dm2e.eu
Europeana Channels
Semantic auto-completion

23. Not only end-user facing functions
Data must be accessible
(Unified) APIs, Linked Data
Data re-users should be able to provide enhanced services
to their audience easily, especially in digital humanities
Specific collection and application needs cannot rely on a handful of
generic vocabularies

24. Work needed

25. Vocabulary management and publication
 Europeana developed its own WWI vocabulary based on a
subset of LCSH
Terms translated in 10 languages and linked to id.loc.gov

26. Vocabulary services
http://data.europeana.eu/concept/loc/sh85148236

27. Representing finer-grained semantics
 More precise relationships and formal semantics
 For query expansion or data validation
 E.g. ISO 25964 and Getty SKOS extensions

28. Representing finer-grained semantics
Depth level, concept associations
XKOS
Pre-coordinated strings
MADS/RDF

29. Representing finer-grained semantics?
Finer-grained semantics can be useful, but core models
are key
They are what most people will start using

30. The need for alignment / co-reference /
reconciliation
KOS 1:
animals
cats
wildcats
KOS 2:
animal
human
object

31. A lot of work (being) done
 A long line of work in the KOS community: DESIRE,
CARMEN, Renardus, LIMBER, HILT, MSAC, MACS,
Crisscross, KoMoHe, FAO…
 Continued in Linked data context: Pleiades, Wikidata…
MACS: 120K links between Library of Congress Subject Headings (LCSH),
RAMEAU, Schlagwortnormdatei (SWD)

32. Semantic mismatches
Irish vocabulary
From: Runar Bergheim
Norwegian
vocabulary
skos:exactMatch

33. Requires flexible approaches
 AMALGAME/CultuurLink:
http://semanticweb.cs.vu.nl/amalgame/
http://cultuurlink.beeldengeluid.nl/

34. Finding and re-using vocabularies
Well-known or new vocabularies
Wikidata, VIAF, Geonames, Pleiades, DBpedia, LCSH…
Data repositories and inventories
The Data Hub

35. Vocabulary selection criteria
 Available in technically appropriate way
 Well-maintained
 Documented (including metadata)
 Well-connected, e.g. equivalent elements in other
vocabularies are indicated
 Multilingual
 Open
• license stacking hampers re-use
Quality assessment?
Cf. Data on the Web Best Practices
http://www.w3.org/TR/2015/WD-dwbp-20150625/#dataVocabularies

36. Take-home messages
Efforts across the whole ecosystem
Publishers of vocabularies, Providers of object data, Application
developers, Researchers…
Requires to get very different steps right
Implementing standards for data exchange
Design consuming applications
Not only technical: encouraging open data!

37. Thank you!
Antoine Isaac
antoine.isaac@europeana.eu