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Package-based Description Logics – Preliminary Results

Package-based Description Logics – Preliminary Results

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Package-based Description Logics – Preliminary Results

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  1. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 1

  2. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 2

  3. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 3

  4. A Distributed Semantic Web Berners-Lee, T., Hendler, J., and Lassila, O. (2001).The semantic web. Scientific American, 284(5):34-43. International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 4

  5. Collaborative building of an animal trait ontology that involves multiple research groups across the world Swine Horse Each group works on an ontology module for a particular species (according to the group’s best expertise) Cattle Chicken A COB Example International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 5

  6. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 6

  7. Modular Ontology Languages Today 2002 2003 2004 2005 2006 DDL based CTXWL C-OWL ? OWL E-Connections (E-connection can also work other logics e.g. modal logic) (to be discussed at the WoMO workshop) P-DL Our approach International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 7

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

  9. Expressivity Comparison [Baot et al. ASWC 2006] International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 9

  10. 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? International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 10

  11. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 11

  12. Animal ontology Dog General General Pet PetDog Pet Wild Livestock 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 • PC: Package extension with only concept name importing • E.g., SHOIQP= SHOIQ +P ALCPC = ALC + PC International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 12

  13. O1 (General Animal) O2 (Pet) It uses ALCP, but not ALCPC Package: Example International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 13

  14. P3 P P 2 2 private private public public P P 1 1 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 14

  15. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 15

  16. Localized Semantics O1 O2 AnimalI 2 AnimalI DogI 1 2 CarnivoreI 1 DogFoodI 2 PetDogI DogI 2 PetI 1 2 eatsI 2 x fooI 2 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 16

  17. O1 O2 importing Semantics of Importing AnimalI 2 AnimalI 1 DogI CarnivoreI 2 1 DogFoodI 2 PetDogI DogI 2 PetI 1 2 eatsI 2 x x fooI 2 Image domain relation International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 17

  18. AnimalI g CarnivoreI g DogI g DogFoodI g PetDogI I g eatsI g x fooI g PetI g Global Interpretations • The (conceptual) global interpretation for the (virtually) integrated ontology • It can be combined from local interpretations International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 18

  19. r12 ΔI1 ΔI2 x’ x CI2 CI1 x r13 r23 CI x’’ CI3 Global interpretation obtained from local Interpretations by merging shared individuals ΔI3 Partially Overlapped Model bijective (one-to-one) Transitive (Compositional consistent) International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 19

  20. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 20

  21. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 21

  22. 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 ? International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 22

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

  24. 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) (4) (3) (2) International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 24

  25. (x) T3 L1(x)={A⊔B A, B } L2(x)={B⊔C C, B} (x) r(x,B) (x) x r(x,C) r(x,A) T2 T1 x x • P1: 1:A 1:B • P2: 1:B 2:C • P3: 2:C 3:D • Query: if A D (witnessed by P3) ALCPC Expansion Example L3(x)={A⊓D, C⊔D A,C, D} ,B • 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 Transitive Subsumption Propagation International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 25

  26. x1 {A1,B1} x2 x3 {B2} {A2} x4 {A3,B3} x1 x1 {B1} {A1} rA rA rB rB x2 x3 {B2} {A2} rB rB x4 x4 {A3} {B3} The (conceptual) global tableau Local Reasoner for package A Local Reasoner for package B ALCPC Expansion Example (2) International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 26

  27. More complex situations [Bao & Honavar, WI2006] • Cyclic name importing • Asynchronous parallel reasoning [Bao etal, (to be submitted)] • Role, nominal importing • Component languages in SHOIQ International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 27

  28. Ongoing: Concealable Reasoning • A reasoner should not expose hidden knowledge • However, such hidden knowledge may still be (indirectly) used in safe queries. Yes Queries Unknown International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 28

  29. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 29

  30. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 30

  31. The COB Editor Pig Package Cattle Package Chicken Package http://sourceforge.net/projects/cob/ International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 31

  32. WikiOnt 2 (under development) A Wiki-based Ontology Editor with GUI Will be on http://sourceforge.net/projects/wikiont/ International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 32

  33. Outline • Motivation • Language Features • Semantics • Reasoning • Applications • Conclusions International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 33

  34. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 34

  35. Ongoing work • Reasoning with OWL (SHOIQ) + Package extension • Reasoning with selectively hidden knowledge • The implementation of the distributed reasoner (based on Pellet) • WikiOnt 2 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 35

  36. 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 International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 36

  37. Publications Reasoning • 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). • 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 • 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. • 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. International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 37

  38. References (Related Work) DDL: • A. Borgida and L. Serafini. Distributed description logics: Directed domain correspondences in federated information sources. InCoopIS/DOA/ODBASE, pages 36-53, 2002. • 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. • L. Serafini, A. Borgida, and A. Tamilin. Aspects of distributed and modular ontology reasoning. In IJCAI, pages 570-575, 2005 • L. Serafini and A. Tamilin. Local tableaux for reasoning in distributed description logics. In Description Logics Workshop 2004, CEUR-WS Vol 104, 2004. • L. Serafini and A. Tamilin. Drago: Distributed reasoning architecture for the semantic web. In ESWC, pages 361-376, 2005. E-Connections: • B. C. Grau. Combination and Integration of Ontologies on the Semantic Web. PhD thesis, Dpto. de Informatica, Universitat de Valencia, Spain, 2005. • O. Kutz, C. Lutz, F. Wolter, and M. Zakharyaschev. E-connections of abstract description systems. Artif. Intell., 156(1):1-73, 2004. International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 38

  39. Thanks! International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 39

  40. SLM: example PackagePackage Hierarchy Scope Limitation A schedule ontology Visible: there is an activity Hidden: details of the activity [CTS06 Paper] a.k.a [1] International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 40

  41. Ontology: AnimalI DogI Interpretation: In any world (or called model) that conforms to the ontology DogFoodI goofyI eatsI • For any instance x of Dog, x is also an instance of Animal. • There is a y in the world, that a Dog x eats y and y is a DogFood • The individual goofy in the world is a Dog. DL Interpretation - Example International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 41

  42. Messages y y T1 T2 {C?} C(y) y y T1 T2 {C} International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 42

  43. Tableau Expansion Tableau Expansion for ALCPC with acyclic concept importing More expressive extensions in action: SHOIQ + P International Semantic Web Conference (ISWC) 2006. Doctoral Consortium Track, Nov 5, 2006 Athens, GA 43