Package-based Description Logics – Preliminary Results
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Package-based Description Logics – Preliminary Results






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Package-based Description Logics – Preliminary Results Package-based Description Logics – Preliminary Results Presentation Transcript

  • 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:
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • 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
  • A Distributed Semantic Web Berners-Lee, T., Hendler, J., and Lassila, O. (2001).The semantic web. Scientific American, 284(5):34-43.
  • A COB Example Swine Cattle Chicken 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
  • 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
  • Modular Ontology Languages Today OWL 2002 2003 2004 2005 2006 C-OWL CTXWL E-Connections Our approach DDL based ? (E-connection can also work other logics e.g. modal logic) P-DL (to be discussed at the WoMO workshop)
  • 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)
  • Expressivity Comparison [Baot et al. ASWC 2006]
  • 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?
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • 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 Wild Livestock Animal ontology PetDog Pet Dog General
  • Package: Example O 1 (General Animal) O 2 (Pet) It uses ALCP, but not ALCP C
  • 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
    P 3 P 1 P 2 public private P 1 P 2 public private
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • Localized Semantics O 1 O 2 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
  • Semantics of 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 O 1 O 2 importing
  • Global Interpretations
    • The (conceptual) global interpretation for the (virtually) integrated ontology
    • It can be combined from local 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
  • Partially Overlapped Model bijective (one-to-one) Transitive (Compositional consistent) Δ I 1 Δ I 2 x x’ C I 1 C I 2 r 12 Δ I 3 r 13 r 23 x’’ C I 3 x C I Global interpretation obtained from local Interpretations by merging shared individuals
  • 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
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • 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 ?
  • Distributed Reasoning 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.
    Stan: So they are far from us. Too Bad. Stan: Hey, Chef . Is Kyle’s new home far from us? Cartman: San Francisco, I guess.
  • 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)
  • ALCP C Expansion Example L 3 (x)={ A⊓  D ,  C⊔D A,  C,  D} 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 T 3 x
    • 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 )
    r(x,  C ) x x r(x,A) T 2 T 1 L 2 (x)={  B⊔C  C ,  B} L 1 (x)={  A⊔B A , B } r(x,  B )  (x)  (x)  (x)
  • ALCP C Expansion Example (2) x 1 {A 1 } x 1 {B 1 } {A 3 } x 4 Local Reasoner for package A Local Reasoner for package B {A 2 } x 2 r A {B 2 } x 3 r B {B 3 } x 4 r B x 1 {A 1 ,B 1 } {A 2 } {A 3 ,B 3 } {B 2 } x 2 x 3 x 4 The (conceptual) global tableau r A r B r B
  • More complex situations
    • [Bao & Honavar, WI2006]
    • Cyclic name importing
    • Asynchronous parallel reasoning
    • [Bao etal, (to be submitted)]
    • Role, nominal importing
    • Component languages in SHOIQ
  • 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
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • 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
  • The COB Editor Pig Package Cattle Package Chicken Package
  • WikiOnt 2 (under development) A Wiki-based Ontology Editor with GUI Will be on
  • Outline
    • Motivation
    • Language Features
    • Semantics
    • Reasoning
    • Applications
    • Conclusions
  • 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
  • Ongoing work
    • Reasoning with OWL (SHOIQ) + Package extension
    • Reasoning with selectively hidden knowledge
    • The implementation of the distributed reasoner (based on Pellet)
    • WikiOnt 2
  • 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.
  • 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.
  • 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.
    • Thanks!
  • 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
  • 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
  • Messages y y {C?} T 1 T 2 y y {C} C(y) T 1 T 2
  • Tableau Expansion Tableau Expansion for ALCP C with acyclic concept importing More expressive extensions in action: SHOIQ + P