1. 1 Ontology Evolution within Ontology Editors Presentation at EKAW, Sigüenza, October 2002 L. Stojanovic, B. Motik FZI Research Center for Information Technologies at the University of Karlsruhe, Germany

2. 2 Agenda Introduction Requirements Evaluation Conclusion

3. 3 Introduction Ontology editors are main tools for ontology development Ontologies must be able to evolve for a number of reasons, including the following:  Application domains and user‘s needs are changing  System can be improved An ontology editor has to support ontology evolution

4. 4 Agenda Introduction Requirements Evaluation Conclusion

5. 5 Requirements for Ontology Evolution Functional requirement User’s supervision requirement Transparency requirement Reversibility requirement Auditing requirement Ontology refinement requirement Usability requirement

6. 6 Functional requirement - specifies which functionality must be provided for the ontology development and evolution - depends on the underlying ontology model

7. 7 Functional requirement Composite changes  They are more powerful  They have coarser granularity  They have often more meaningful semantics e.g. Move_Concept  (RemoveSubConcept + AddSubConcept)

8. 8 Functional requirement

9. 9 User‘s supervision requirement ProjectPerson Student HiwiPhDStudent X Critical situations:  how to handle orphaned concepts;  how to handle orphaned properties;  how to propagate properties to the concept whose parent changes;  what constitutes a valid domain of a property;  what constitutes a valid range of a property;  whether a domain (range) of a property can contain a concept that is at the same; time a subconcept of some other domain (range) concept;  the allowed shape of the concept hierarchy;  the allowed shape of the property hierarchy;  must instances be consistent with the ontology. - enables the user-driven process of change resolving - delete - reconnect to the root - reconnect to the superconcepts

10. 10 Transparency requirement - provides a human-computer interaction for evolution by: presenting change information in an orderly way allowing easy spotting of potential problems alleviating the understanding of the scope of the change

11. 11 Reversibility requirement Remove Concept Add Concept X - states that an ontology editor has to allow undoing changes at the user’s request

12. 12 Auditing requirement - allows inspecting the performed changes by: keeping a detailed log of all performed changes associating meta information with each log change tracking the identity of the change author

13. 13 Structure-driven –exploits a set of heuristics to improve an ontology based on the analysis of the ontology structure Data-driven - detects the changes based on the analysis of the ontology instances Usage-driven – takes into account the usage of the ontology If no instance of a concept C use any of the properties defined for C, but only properties inherited from the parent concept, we can make an assumption that C is not necessary. By tracking when entity has last been retrieved by a query, it may be possible to discover that some entities are out of date Ontology refinement requirement  If all subconcepts have the same property, the property may be moved to the parent concept  A concept with a single subconcept should be merged with its subconcept.  If a direct parent of a concept can be achieved though a non- direct path, then the direct link should be deleted.

14. 14 Usability requirement - states that an ontology editor should: be ergonomically correct to minimise human errors detect logical conflicts (verification) provide the means for validation

15. 15 Agenda Introduction Requirements Evaluation Conclusion

16. 16 Evaluation “-“ - no support “<>” – partial support “+” - full support

17. 17 Agenda Introduction Requirements Evaluation Conclusion

18. 18 Conclusion Ontology editors should: enrich the list of possible changes enable the customisation of the change resolving inform the user about all effects of a change allow undoing changes allow inspecting the performed changes suggest the user to generate a change identify inconsistency and provide answers to the questions such as how, why, what if, etc.

19. 19 Resolution points Elementary evolution strategies http://kaon.semanticweb.org

20. 20 Thanks! Any questions? L. Stojanovic, B. Motik FZI Research Center for Information Technologies at the University of Karlsruhe, Germany http://wim.fzi.de/wim