This presentation discusses approaches to integrating ontologies based on an EDM (Europeana Data Model) framework. It outlines four methods for reusing ontologies - direct adoption, reuse with new URIs, reuse by establishing sub-relations, and reuse through equivalence properties. The presentation then examines how these methods have been applied in the EDM and in a related project (DM2E), emphasizing a mixture of approaches is often best to avoid contradictory descriptions while maximizing reuse.

1. Towards Integrating Ontologies
An EDM-Based Approach
Evelyn Dröge, Julia Iwanowa, Violeta Trkulja, Steffen Hennicke, Stefan Gradmann
Berlin School for Library and Information Science, Humboldt-Universität zu Berlin
Presentation on the 13th International Symposium of Information Science
Potsdam, 21.03.2013
co-funded by the European Union

2. DM2E project
Digitised Manuscripts to Europeana (DM2E)
• EU-funded Europeana satelite project
• Duration: Three years (2012 – 2015)
• Partners from Germany, Austria, Norway, Greece, UK and Italy
• Primary aims: To enable as many content providers as possible
to get their data into Europeana and to stimulate the creation of
new tools and services for reuse of Europeana data in the
Digital Humanities
IBI at the Humboldt-Universität zu Berlin
• Coordinates the project
• Is further involved in modeling and in evolving the technical
infrastructure
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3. DM2E: Interoperability approach
• Base: Semantic Web and Linked Data
– Enable and facilitate data interoperability
– Share and reuse ontologies
• Build on common data models
– EDM, DC and DCTerms, OAI-ORE, CIDOC-CRM, FOAF, SKOS
– BIBO, VOID, FABIO
• Uses W3C standards
– RDF(S), OWL
 Enable data interoperability
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4. Why should we reuse ontologies?
• Nature of Linked Data
• Reduce multiple likewise resources
• Better visibility of the ontology
• Better quality of the ontology
• Better integration into the Linked Open Data Cloud
• Easy access for more applications
• Make it easier for others to reuse the vocabulary
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5. Reuse practice
• Three steps workflow
1. Ontology retrieval
2. Integration-oriented ontology evaluation
 Identification of suitable classes and properties
 Analysis of missing elements
3. Ontology integration
 Different methods
Simperl, 2010
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6. Steps in the Reuse Workflow

7. Step 1: Ontology retrieval
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8. Step 2: Integration-oriented ontology evaluation
DC • Which elements are
missing or can be
rdaGr2 DCTerms replaced?
• What are suitable
EDM SKOS classes or properties
in other standards or
FOAF vocabularies?
ORE
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9. Step 3: Ontology integration
Four different methods can be used for reusing ontologies:
1. Direct adoption of external resources
• External classes or properties are directly used in the ontology buildup.
• Can be used if the external class or property exactly matches the own resource.
• Definitions or labels should not be adjusted!
2. Reuse of external resources without original URIs
• The name of a foreign property or class is used without its original namespace.
3. Reuse of external resources with integration into ontology hierarchy
• Properties or classes are created in the own namespace.
• Subproperty or subclass relations are built between them and the external
resource.
4. Referring to external resources via equivalence properties
•owl:equivalentClass or owl:equivalentProperty are used to refer to
equivalent external resources.
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10. Integrating ontologies:
Method comparison
3
Indirect
Integration
4
Direct 2
1
Integration
Original URI New URI
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11. Further Insight into the Integration Methods

12. 1. Method:
Direct adoption of external resources
• Example: dm2edata:exampleItem
edm:type text ;
bibo:isbn „978-3-86680-192-9“ .
 Integrating bibo properties for describing text objects
• When should the method be used?
– If the meaning and definition of the external resource is identical
to the meaning of the own resource.
• Advantages and Disadvantages
+ Pro: Reduces the amount of resources that describe the same
thing in other words.
− Con: The method is also used when the meaning is not exactly the
same, which can lead to conflicting descriptions.
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13. 1. Method:
Direct adoption of external resources
Example: foaf:Document
Document
Physical Thing ?
Dokument
Abstract Class ?
Document@en
Electronic?
Documents
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14. 1. Method:
Direct adoption of external resources
Example: Some properties of foaf:Document
rdfs:label Document
Document@en Retrieved from the Linked Open
Documentation@en Vocabularies SPARQL endpoint:
document@en
http://lov.okfn.org/endpoint/lov
dc:title Document@en
dcterms:identifier foaf:Documentation @en-gb
rdfs:comment A document.
An abstract class defining any kinds of publishing work.@en
The foaf:Document class fully represents the ADMS concept of documentation.@en
Similar to the Agent concept, we have again decided to include a concept from the
popular FOAF ontology. The FOAF Vocabulary Specification currently defines
Document in a very loose way: The foaf:Document class represents those things
which are, broadly conceived, 'documents'. ... We do not (currently) distinguish
between physical and electronic documents, or between copies of a work and the
abstraction those copies embody." […]
vann:usageNote Used in ADMS specifically for the class of documents that further describe a Semantic
Asset or give guidelines for its use. ADMS expects all documents to have a title (use
dcterms:title).^^
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15. 2. Method: Reuse with new URIs
• Example: Different URIs for the class thing
owl:Thing
gold:Thing
 Are they identical or equivalent?
• Advantages and Disadvantages
+ Pro: Can be used as a first step in the construction process if other
vocabularies are not known.
− Con: It is not clear how the different classes can be set into
relation and it makes it hard to query or reuse the vocabulary.
• This method should not be used!
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16. 3. Method: Reuse with subrelations
• Example: dm2e:Agent rdfs:subClassOf foaf:Agent .
dm2e:publishedAt rdfs:subPropertyOf
dcterms:spatial .
 New dm2e property and class as subelements
• When should this method be used?
– If an existing class or property is found which is broader defined
than the resource that should be created.
• Advantages and Disadvantages
+ Pro: The new property or class can have its own description.
+ Pro: Broader properties or classes are easy to be found in upper
ontologies .
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17. 4. Method: Reuse with equivalence properties
• Example: edm:Event owl:equivalentClass
crm:E4.Period .
prism:issn owl:equivalentProperty
bibo:issn .
 Reference to equivalent resources
• When should this method be used?
– If exactly the same individuals can be part of all equivalent classes
or can be connected with all equivalent properties.
• Advantages and Disadvantages
+ Pro: The elements can have different descriptions.
− Con: Not every tool can interpret the equivalence properties.
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18. Ontology Reuse in DM2E

19. Background: The EDM and its specialisations
The EDM (Europeana Data Model)
… builds the backbone of Europeana
… unites several standards and vocabularies
… covers the representation of cultural heritage objects
from libraries, archives and museums
… is as generic as possible
… can be specialised for different domains
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20. Reusing practice in EDM and DM2E
• Reuse in EDM Primarily used
– Method 1: Direct integration
• Problem: Definitions may differ
– Method 4: Use of equivalence properties
Used for additional classes
• Reuse in DM2E
– Method 1: Direct integration
• Here: Use of additional DM2E scope notes that add information about
the reuse of the integrated element in DM2E
– Method 3: Adding resources with subproperties
• If the new resource has a narrower definition
– Method 4: Use of equivalence properties
• Analogue to the EDM for additional classes or properties
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21. Reusing practice in EDM and DM2E II
• Example: Methods 1 and 3
DC EDM DM2E
dc:contributor dc:contributor dm2e:contributor
rdfs:subPropertyOf
dc:contributor
Range: Not restricted. Range: Person, Range: Person as an URI
organisation or service. of type edm:Agent.
Definition: „An entity that Definition: „An agent that Definition: „A person that
is responsible for making is responsible for making is responsible for making
contributions to the contributions to the contributions to the
resource.“ resource.“ resource.“
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22. Conclusion
• Reuse in DM2E: Mixture of all methods
(excluding method 2)
 Making use of the method that suits best
• There is not one „best method“ for all reuse cases…
… but contradictions in descriptions can be
avoided even if resources are reused!
• What we did not (yet) cover: „When owl:sameAs is not the
same…“
 Problems that might occur when there are too many
different understandings of resource meanings
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23. Thank you for your attention!
Evelyn Dröge
Julia Iwanowa
Berlin School for Library and
Information Science
Humboldt-Universität zu Berlin
www.ibi.hu-berlin.de
Digitised Manuscripts to Europeana
www.dm2e.eu
evelyn.droege@ibi.hu-berlin.de
julia.iwanowa@ibi.hu-berlin.de
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24. References
Literature
• Berners-Lee, T. (2006). Linked Data - Design Issues. W3C Website.
http://www.w3.org/DesignIssues/LinkedData. [03.03.2013]
• Halpin, H., & Hayes, P. J. (2010). When owl:sameAs isn’t the Same: An Analysis of Identity
Links on the Semantic Web. Proceedings of the WWW2010 Workshop on Linked Data on
the Web, LDOW 2010, Raleigh, USA, April 27, 2010, CEUR Workshop Proceedings (Bd.
628).
• Heath, T., & Bizer, C. (2011). Linked Data: Evolving the Web into a Global Data Space.
Synthesis Lectures on the Semantic Web: Theory and Technology (Bd. 1). Morgan &
Claypool.
• Simperl, E. (2010). Guidelines for Reusing Ontologies on the Semantic Web. International
Journal of Semantic Computing, 04(02), 239–283.
Images
• Footstep (Slide 6): http://openclipart.org/detail/left-footprint-by-anonymous
• Magnifier (Slide 11): http://openclipart.org/detail/159469/web-search-grayscale-by-
sibskull
• Document (Slide 13): http://info.docuvantage.com/Portals/61671/images/stack%20of%
20files%20photo_istock.jpg
• Ontology (Slide 19): http://openclipart.org/detail/133363/ontology-by-imad
• IBI (Slide 23): http://commons.wikimedia.org/wiki/File:Berlin,_Mitte,_Dorotheenstrasse,
_Handelskammer_Berlin_02.jpg
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