1. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA1 Package-based Description Logics – Preliminary Results Jie Bao, Doina Caragea, Vasant Honavar Artificial Intelligence Research Laboratory Computer Science Department Iowa State University Ames, IA USA 50011 Email: baojie@cs.iastate.edu

2. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA2 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

3. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA3 Modular Ontologies What is modular ontology? –An ontology that contains a set of smaller, (semantically) connected component ontologies Why modular ontology ? –A Distributed Semantic Web –Collaborative Ontology Building (COB) –Selective Ontology Reuse –Large Ontology Storage and Reasoning

4. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA4 Berners-Lee, T., Hendler, J., and Lassila, O. (2001).The semantic web. Scientific American, 284(5):34-43. A Distributed Semantic Web

5. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA5 A COB Example Swine CattleChicken Horse Each group works on an ontology module for a particular species (according to the group’s best expertise) Collaborative building of an animal trait ontology that involves multiple research groups across the world

6. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA6 Ontology Languages Needed Has localized semantics –Allows distributed reasoning Supports fine-grained ontology organizational structure –Allows partial ontology reuse –Supports selective knowledge hiding Enables collaborative and scalable tools

7. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA7 Modular Ontology Languages Today OWL 2002 2003 2004 2005 2006 C-OWL CTXWL E-Connections Our approach DDL based ? ? (E-connection can also w ork other logics e.g. mod al logic) P-DL (to be discussed at the WoMO workshop)

8. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA8 Modular Ontology Languages Today (2) E-Connections –Connects DL modules with special types of roles called “links” PetOwner Pet owns Distributed Description Logics (DDL) & C-OWL –Allows “bridge rules” between concepts across ontology modules Pet Animal Dog (onto) (into)

9. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA9 Expressivity Comparison [Baot et al. ASWC 2006]

10. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA10 Open problems How to obtain stronger expressiveness? How to enable distributed reasoning without required global knowledge? How to ensure the reasoning exactness w.r.t. standard reasoning with integrated ontology? How to create modular ontologies?

11. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA11 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

12. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA12 Package Packages of an ontology –Are defined in subsets of the same decidable DL,e.g., SHOIQ –May contain both local terms and imported terms; Each term has a home package P :Package extension –P C : Package extension with only concept name importing –E.g., SHOIQP= SHOIQ +P ALCP C = ALC + P C General Pet WildLivestock Animal ontology PetDog Pet Dog General

13. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA13 Package: Example O 1 (General Animal)O 2 (Pet) It uses ALCP, but not ALCP C

14. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA14 Ongoing work: Scope Limitation SLM of an ontology term or axiom t –is a boolean function that defines the visible scope of a term or axiom. Example SLMs –Public (t,r): t is accessible from anywhere –Private (t,r): t is only available in the home package P3P3 P 1 P 2 public private P 1 P 2 public private

15. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA15 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

16. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA16 Localized Semantics O1O1 O2O2 Animal I Carnivore I Dog I foo I Dog I Pet I PetDog I x eats I 1 1 1 2 2 2 2 2 DogFood I 2 Animal I 2

17. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA17 Semantics of Importing O1O1 O2O2 importing Animal I Carnivore I Dog I x foo I Dog I Pet I PetDog I x eats I 1 1 1 2 2 2 2 2 DogFood I 2 Animal I 2 Image domain relation

18. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA18 Global Interpretations Animal I Carnivore I Dog I I PetDog I x Pet I eats I g g g g g g foo I g DogFood I g The (conceptual) global interpretation for the (virtually) integrated ontology It can be combined from local interpretations

19. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA19 Partially Overlapped Model ΔI1ΔI1 ΔI2ΔI2 x x’ CI1CI1 CI2CI2 r 12 ΔI3ΔI3 r 13 r 23 x’’ CI3CI3 x CICI Global interpretation obtained from local Interpretations by merging shared individuals bijective (one-to-one) Transitive (Compositional consistent)

20. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA20 P-DL Semantics Features Localized Semantics –Local “top” concepts are not the same –Each package explains the world based on its transitive importing closure (local point of view). Stronger expressivity –Supports both inter-module concept subsumption and inter-module role usage. Decidable (when all modules are from the same decidable DL) Solves some reasoning diffculities in other approaches

21. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA21 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

22. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA22 Reasoning for Modular Ontology Major Consideration: should not require the integration of ontology modules. –High communication cost –High local memory cost –May violate module autonomy, e.g., privacy Question: can we do reasoning for P-DL without –(syntactic level) an integrated ontology ? –(semantic level) a (materialized) global tableau ?

23. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA23 Distributed Reasoning Stan: Hey, Chef. Is Kyle’s new home far from us? Chef: Hello there, children! Where does Kyle move to? Cartman: San Francisco, I guess. Chef: We are in South Park, Colorado; San Francisco is in California; Colorado is far from California. Stan: So they are far from us. Too Bad.

24. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA24 Federated Reasoning for P-DL Basic strategy Use multiple local reasoners, each for a single package Each local reasoner creates and maintains a local tableau based on (only) local knowledge A local reasoner may query other reasoners if its local knowledge is incomplete Global relation among tableaux is created by messages (1) (2) (3) (4)

25. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA25 T3T3 x ALCP C Expansion Example P 1 : 1:A 1:B P 2 : 1:B 2:C P 3 : 2:C 3:D Query: if A D (witnessed by P 3 ) L 3 (x)={A ⊓  D,  C ⊔ D A,  C,  D} r(x,  C ) x x r(x,A) T2T2 T1T1 L 2 (x)={  B ⊔ C  C,  B} L 1 (x)={  A ⊔ B A, B } r(x,  B )  (x) Transitive Subsumption Propagation Messages: m(x,C): if copy of x has label C r(x,C): add C into the label of x (or its copy) Message Target: C’s home package reasoner, B, B

26. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA26 ALCP C Expansion Example (2) x1x1 {A 1 } x1x1 {B 1 } {A 3 } x4x4 Local Reasoner for package A Local Reasoner for package B {A 2 } x2x2 rArA {B 2 } x3x3 rBrB {B 3 } x4x4 rBrB x1x1 {A 1,B 1 } {A 2 } {A 3,B 3 } {B 2 } x2x2 x3x3 x4x4 The (conceptual) global tableau rArA rBrB rBrB

27. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA27 More complex situations [Bao & Honavar, WI2006] Cyclic name importing Asynchronous parallel reasoning [Bao etal, (to be submitted)] Role, nominal importing Component languages in SHOIQ

28. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA28 Ongoing: Concealable Reasoning A reasoner should not expose hidden knowledge However, such hidden knowledge may still be (indirectly) used in safe queries. Queries Yes Unknown

29. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA29 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

30. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA30 Collaborative Ontology Building Ontology modularity facilitates collaborative building Each package can be independently developed Multiple users can concurrently edit the ontology on different packages Ontology can be only partially loaded Unwanted interactions are minimized by limiting term and axiom visibility

31. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA31 The COB Editor Pig Package Cattle Package Chicken Package http://sourceforge.net/projects/cob/

32. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA32 WikiOnt 2 (under development) A Wiki-based Ontology Editor with GUI Will be on http://sourceforge.net/projects/wikiont/

33. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA33 Outline Motivation Language Features Semantics Reasoning Applications Conclusions

34. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA34 Main Contributions Investigate the requirement and formal semantics of modular ontologies Present a formal modular ontology language, P-DL, that can overcome many limitations in existing approaches –Stronger expressivity –Solve some inference difficulties Present a federated reasoning algorithm for P-DL that can –strictly avoid integration of ontology modules –handle reasoning tasks not solvable in existing approaches Apply the notion of modular ontology in collaborative ontology building

35. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA35 Ongoing work Reasoning with OWL (SHOIQ) + Package extension Reasoning with selectively hidden knowledge The implementation of the distributed reasoner (based on Pellet) WikiOnt 2

36. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA36 Publications Language Features Bao, J.; Caragea, D.; and Honavar, V. (2006) Towards collaborative environments for ontology construction and sharing. In International Symposium on Collaborative Technologies and Systems (CTS 2006). IEEE Press. 99–108. Semantics Bao, J.; Caragea, D.; and Honavar, V. (2006) Modular ontologies - a formal investigation of semantics and expressivity. In R. Mizoguchi, Z. Shi, and F. Giunchiglia (Eds.): Asian Semantic Web Conference 2006, LNCS 4185, 616–631. Bao, J.; Caragea, D.; and Honavar, V. (2006) On the semantics of linking and importing in modular ontologies. In I. Cruz et al. (Eds.): ISWC 2006, LNCS 4273. 72–86. http://boole.cs.iastate.edu:9090/popeye/Wiki.jsp?page=Academic.Basic.CV.Publication

37. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA37 Publications Reasoning 5.Bao, J.; Caragea, D.; and Honavar, V. (2006) A tableau-based federated reasoning algorithm for modular ontologies. 2006 IEEE/WIC/ACM International Conference on Web Intelligence (In Press). 6.Bao, J.; Caragea, D.; and Honavar, V. (2006) A distributed tableau algorithm for package-based description logics. In the 2nd International Workshop On Context Representation And Reasoning (CRR 2006). Collaborative Ontology Building 7.Bao, J.; and Honavar, V. (2004) Collaborative ontology building with WikiOnt - a multi-agent based ontology building environment. In Proc. of 3rd International Workshop on Evaluation of Ontology-based Tools, at ISWC 2004, pages 37–46. 8.Bao, J.; Hu, Z.; Caragea, D.; Reecy, J.; and Honavar, V. (2006) Developing frameworks and tools for collaborative building of large biological ontologies. In The 4th International Workshop on Biological Data Management (BIDM’06). 191-195.

38. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA38 References (Related Work) DDL: 9.A. Borgida and L. Serafini. Distributed description logics: Directed domain correspondences in federated information sources. InCoopIS/DOA/ODBASE, pages 36-53, 2002. 10.P. Bouquet, F. Giunchiglia, and F. van Harmelen. C-OWL: Contextualizing ontologies. In Second International Semantic Web Conference, volume 2870 of Lecture Notes in Computer Science, pages 164-179. Springer Verlag, 2003. 11.L. Serafini, A. Borgida, and A. Tamilin. Aspects of distributed and modular ontology reasoning. In IJCAI, pages 570-575, 2005 12.L. Serafini and A. Tamilin. Local tableaux for reasoning in distributed description logics. In Description Logics Workshop 2004, CEUR-WS Vol 104, 2004. 13.L. Serafini and A. Tamilin. Drago: Distributed reasoning architecture for the semantic web. In ESWC, pages 361-376, 2005. E-Connections: 14.B. C. Grau. Combination and Integration of Ontologies on the Semantic Web. PhD thesis, Dpto. de Informatica, Universitat de Valencia, Spain, 2005. 15.O. Kutz, C. Lutz, F. Wolter, and M. Zakharyaschev. E-connections of abstract description systems. Artif. Intell., 156(1):1-73, 2004.

39. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA39 Thanks!

40. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA40 SLM: example A schedule ontology Hidden: details of the activity Visible: there is an activity [CTS06 Paper] a.k.a [1] Package Package Hierarchy Scope Limitation

41. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA41 DL Interpretation - Example Interpretation: In any world (or called model) that conforms to the ontology Ontology: Dog I Animal I For any instance x of Dog, x is also an instance of Animal. goofy I The individual goofy in the world is a Dog. eats I There is a y in the world, that a Dog x eats y and y is a DogFood DogFood I

42. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA42 Messages y y {C?} T1T1 T2T2 y y {C}{C} C(y) T1T1 T2T2

43. Iowa State University Department of Computer Science Artificial Intelligence Research Laboratory International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA43 Tableau Expansion Tableau Expansion for ALCP C with acyclic concept importing More expressive extensions in action: SHOIQ + P