Towards Integrating Ontologies An EDM-Based Approach

co-funded by the European Union

Towards Integrating Ontologies

An EDM-Based Approach

Evelyn Dröge, Julia Iwanowa, Violeta Trkulja, Steffen Hennicke, Stefan GradmannBerlin School for Library and Information Science, Humboldt-Universität zu Berlin

Presentation on the 13th International Symposium of Information SciencePotsdam, 21.03.2013

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

Towards Integrating Ontologies: An EDM-Based Approach 221.03.2013

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


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


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

Steps in the Reuse Workflow

Step 1: Ontology retrieval


Step 2: Integration-oriented ontology evaluation

EDM

DC

DCTerms

SKOS

FOAF

ORE

rdaGr2


• Which elements are

missing or can be

replaced?

• What are suitable

classes or properties

in other standards or

vocabularies?

Step 3: Ontology integration

Four different methods can be used for reusing ontologies:


• 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!

1. Direct adoption of external resources

• The name of a foreign property or class is used without its original namespace.

2. Reuse of external resources without original URIs

• Properties or classes are created in the own namespace.

• Subproperty or subclass relations are built between them and the external resource.

3. Reuse of external resources with integration into ontology hierarchy

•owl:equivalentClass or owl:equivalentProperty are used to refer to equivalent external resources.

4. Referring to external resources via equivalence properties

Integrating ontologies:Method comparison


Original URI New URI

IndirectIntegration

DirectIntegration

4

1 2

3

Further Insight into the Integration Methods

1. Method:Direct adoption of external resources

• Example:

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.


dm2edata:exampleItem

edm:type text ;

bibo:isbn „978-3-86680-192-9“ .


Example: foaf:Document


Document

Dokument

Document@en

Documents

Physical Thing ?

Abstract Class ?

Electronic?

Example: Some properties of foaf:Document



rdfs:label DocumentDocument@enDocumentation@endocument@en

dc:title Document@endcterms:identifier foaf:Documentation @en-gb

rdfs:comment A document.An abstract class defining any kinds of publishing work.@enThe foaf:Document class fully represents the ADMS concept of documentation.@enSimilar to the Agent concept, we have again decided to include a concept from thepopular FOAF ontology. The FOAF Vocabulary Specification currently definesDocument in a very loose way: The foaf:Document class represents those thingswhich are, broadly conceived, 'documents'. ... We do not (currently) distinguishbetween physical and electronic documents, or between copies of a work and theabstraction those copies embody." […]

vann:usageNote Used in ADMS specifically for the class of documents that further describe a SemanticAsset or give guidelines for its use. ADMS expects all documents to have a title (usedcterms:title).^^

Retrieved from the Linked Open Vocabularies SPARQL endpoint:http://lov.okfn.org/endpoint/lov

2. Method: Reuse with new URIs


• Example: Different URIs for the class 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!

owl:Thing

gold:Thing

3. Method: Reuse with subrelations


• Example:

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 .

dm2e:Agent rdfs:subClassOf foaf:Agent .

dm2e:publishedAt rdfs:subPropertyOf

dcterms:spatial .

4. Method: Reuse with equivalence properties


• Example:

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.

edm:Event owl:equivalentClass

crm:E4.Period .

prism:issn owl:equivalentProperty

bibo:issn .

Ontology Reuse in DM2E

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


Reusing practice in EDM and DM2E


• Reuse in EDM– Method 1: Direct integration

• Problem: Definitions may differ

– Method 4: Use of equivalence properties

• Reuse in DM2E– Method 1: Direct integration

• Here: Use of additional DM2E scope notes that add information aboutthe 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

Primarily used

Used for additional classes

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,

organisation or service.

Range: Person as an URI

of type edm:Agent.

Definition: „An entity that

is responsible for making

contributions to the

resource.“

Definition: „An agent that



resource.“

Definition: „A person that



resource.“

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 beavoided even if resources are reused!

• What we did not (yet) cover: „When owl:sameAs is not thesame…“ Problems that might occur when there are too many

different understandings of resource meanings


Thank you for your attention!

Evelyn DrögeJulia Iwanowa

Berlin School for Library andInformation Science

Humboldt-Universität zu Berlin

www.ibi.hu-berlin.de

Digitised Manuscripts to Europeana

www.dm2e.eu

[email protected]@ibi.hu-berlin.de


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 onthe 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. InternationalJournal 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
