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Combining normal communication with ontology alignment

Combining normal communication with ontology alignment. AAMAS AC 2005 25 July 2005 Utrecht University, the Netherlands Jurriaan van Diggelen, Robbert-Jan Beun, Frank Dignum, Rogier M. van Eijk, John-Jules Meyer. Problem statement Approach Protocols Conclusion. problem.

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Combining normal communication with ontology alignment

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  1. Combining normal communication with ontology alignment AAMAS AC 2005 25 July 2005 Utrecht University, the Netherlands Jurriaan van Diggelen, Robbert-Jan Beun, Frank Dignum, Rogier M. van Eijk, John-Jules Meyer

  2. Problem statement Approach Protocols Conclusion problem Layout of presentation

  3. Inform • … • content:campervan(#93) • … • ontology:cars • … problem Common ontologies Agent 1 Agent 2 Knowledge base Knowledge base Ontology : cars Ontology : cars campervan station wagon campervan station wagon ABox ABox campervan(#93) campervan(#185) campervan(#93)

  4. Inform • … • content:campervan(#93) • … • ontology:cars • … problem What if the receiver doesn’t know the ontology? ? Agent 1 Agent 3 Knowledge base Knowledge base Ontology : cars Ontology : Tourism campervan station wagon RV Hotel ABox ABox campervan(#185) campervan(#93) Currently, this is a burning problem in heterogeneous systems such as the semantic web and open multi agent system

  5. problem Standardization • Develop one ontology and enforce it upon every • agent in the system • Tom Gruber’s definition of ontology: • “Specification of a shared conceptualization” • Problems: • Very large and complex ontology required to suit • the needs of all users. • How do we get every system developer to reach consensus • on which ontology to use (especially in open systems)?

  6. Please translate the message campervan(#93) to ag2’s ontology. • Inform • … • content:RV(#93) • … • ontology:tourism • … Ag OM KB Mapping O cars.campervan tourism.RV problem Ontology mediators: FIPA Ontology Service It’s nice to have someone around that solves your ontology problems… Ag 2 Ag 1 KB KB O : Tourism O : cars RV(#93) ! RV, Hotel, … campervan, … ABox ABox But: - The FIPA Ontology Service is only a specification… - Agents are no longer capable of communicating autonomously.

  7. Agents solve ontology problems among themselves at agent interaction time… S. Bailin & W. Truszkowski (2002) coined the term Ontology Negotiation. problem Ontology negotiation • Most ambitious form of semantic integration. • Much work remains to be done.

  8. We focus on the following issues: Modularity: How are normal agent communication protocols combined with protocols that build up a shared O-cv? Effectivity: O-cv should enable the agents to exchange sufficient information. Simplicity: O-cv should be simple in size and in use. approach Focus

  9. approach Framework • Agents preserve their static private ontologies (O1, O2, O3, O4) . • Intermediate ontology (O-cv) is dynamic and shared. • Sender composes messages by translating private assertions to O-cv. • Receiver interprets messages by translating shared assertions to its private ontology. • Initially O-cv is empty • O-cv is extended when agents negotiate ontologies Ag. 1 Ag. 2 O1 O2 O-cv Ag. 3 Ag. 4 O3 O4

  10. approach lazy alignment Agents should communicate ontological knowledge, only if needed. See if you can manage with the situation as-is. Finish communication only if both agents are satisfied. Normal Communication If communication is not effective, start to negotiate on ontologies Return as soon as possible Communication of ontological knowledge Find a minimal solution which fixes the problem at hand.

  11. If communication is not effective, O-cv must be extended. Communication is considered effective if communication is sound and lossless. Communication is sound if the interpretation of the receiver follows from what the speaker intended to convey. Communication is lossless if no information is lost in the process of translating into and from O-cv. approach What is meant by effective?

  12. vehicle vehicle roadvehicle roadvehicle van van campervan campervan hotel hotel approach God’s eye view ontology defines a god’s eye view over all ontologies in the system. is not known by the agents, it is a way for us to define properties of the system.

  13. Let: be the concept the sender intends to convey be the concept used in the message be the receiver’s interpretation of the message. Communication is sound and lossless iff (soundness) is the most specific concept in for which the above holds (lossless). approach Effective communication formalized

  14. InformExact only succeeds if there is a shared term which is equivalent with what the sender intends to convey. If InformExact does not succeed, the sender adds the concept to O-cv (using concept learning techniques). protocols p1 1 2 Agi: InformExact Agi: AddConcept

  15. vehicle vehicle roadvehicle roadvehicle van van van campervan campervan hotel hotel protocols Example 1 Suppose Ag1 intends to convey van(a) Ag1 : AddConcept(van) Ag1 : InformExact(van(a)) Ag2 interprets this message as roadvehicle(a)

  16. vehicle vehicle roadvehicle roadvehicle van van van campervan campervan hotel hotel protocols Example 2 Suppose Ag2 intends to convey campervan(a)… Dialogue according to P1 Preferred dialogue. Ag2 : AddConcept(campervan) Ag2 : InformExact(campervan(a)) Ag1 : interprets this message as van(a) Ag2 : Inform (van(a)) Ag1 : interprets this message as van(a)

  17. P1 guarantees sound and lossless communication protocols p1 evaluation Pro: Cons: Agents sometimes needlessly teach each other concepts. P1 leads to a bulky O-cv.

  18. An Inform message states the sender’s concept in equal or more general shared concepts. Inform uses the most specific shared concept to convey the sender’s concept. The receiver responds OK if the receiver believes that communication was lossless. Agi: InformExact Agi: Inform Agj: OK 1 2 4 Agi: AddConcept Agj: ReqSpec 3 protocols p2

  19. vehicle vehicle roadvehicle roadvehicle van van van campervan campervan hotel hotel protocols Example 3 Suppose Ag2 intends to convey campervan(a)… Dialogue according to P1 Ag2 : Inform(van(a)) Ag1 : OK (ag1 correctly recognizes lossless communication)

  20. vehicle roadvehicle van campervan campervan hotel protocols Example 4 vehicle vehicle roadvehicle van campervan hotel Suppose Ag2 intends to convey campervan(a)… Ag2 : Inform (vehicle(a)) Ag1 : ReqSpec. (ag1 correctly recognizes that communication may not be lossless) Ag2 : AddConcept(campervan) Ag2 : InformExact(campervan(a)) Ag1 interprets this message as van(a)

  21. vehicle roadvehicle van campervan hotel protocols Example 5 vehicle vehicle roadvehicle van van campervan hotel Suppose Ag2 intends to convey roadvehicle(a)… Ag2 : Inform (vehicle(a)) Ag1 : OK (ag1 correctly recognizes that communication was lossless, because ag1 knows that ag2 has stated its message as precisely as possible; i.e. If ag2 would have known van(a), it would have said so.)

  22. Sender is allowed to state its message in more general terms. Receiver checks if the sender has not stated the message in too general terms by regarding: Whether its own ontology allows more specificic information. What the sender did not say, and therefore did not know either. protocols Summarizing

  23. Agi: InformExact Agi: Inform Agj: OK 1 2 5 Agj: Exit Agj: ReqSpec Agi: AddConcept 4 Agi: Exit 3 Agj: RemoveConcept Agi: RemoveConcept protocols p3 • RemoveConcept removes redundant concepts form the • shared ontology • Redundant concepts don’t add anything to the expressivity • of the shared ontology.

  24. vehicle roadvehicle vehicle roadvehicle van campervan hotel protocols Example 6 vehicle roadvehicle van van campervan hotel Suppose Ag1 intends to convey vehicle(a)… Ag1 : Inform (top(a)) Ag2 : ReqSpec Ag1 : AddConcept(Vehicle) Ag1 : RemoveConcept (RoadVehicle(a)) (This concept is redundant for Ag1)

  25. We have presented ONP’s that Enable lazy ontology alignment Give rise to minimal shared ontology Guarantee sound and lossless communication Read the paper for: Formal semantics of the speech acts. Proofs for lossless communication Thanks for your attention! Conclusion

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