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International Semantic Web Conference ISWC 2006' Doctoral Consortium Track, Nov 5, 2006 Athens, GA1

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Title: International Semantic Web Conference ISWC 2006' Doctoral Consortium Track, Nov 5, 2006 Athens, GA1


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_at_cs.iastate.edu

2
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

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

4
A Distributed Semantic Web
Berners-Lee, T., Hendler, J., and Lassila, O.
(2001).The semantic web. Scientific American,
284(5)34-43.
5
A COB Example
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

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
8
Modular Ontology Languages Today (2)
9
Expressivity Comparison
Baot et al. ASWC 2006
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?

11
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

12
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

13
Package Example
14
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

15
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

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
17
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
18
Global Interpretations
  • The (conceptual) global interpretation for the
    (virtually) integrated ontology
  • It can be combined from local interpretations

19
Partially Overlapped Model
bijective (one-to-one)
Transitive (Compositional consistent)
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

21
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

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
    ?

23
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.

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)
25
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 Cs home package reasoner

Transitive Subsumption Propagation
26
ALCPC Expansion Example (2)
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

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
29
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

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

31
The COB Editor
Pig Package
Cattle Package
Chicken Package
http//sourceforge.net/projects/cob/
32
WikiOnt 2 (under development)
A Wiki-based Ontology Editor with GUI
Will be on http//sourceforge.net/projects/wikiont
/
33
Outline
  • Motivation
  • Language Features
  • Semantics
  • Reasoning
  • Applications
  • Conclusions

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

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

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. 99108.
  • 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, 616631.
  • 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. 7286.

http//boole.cs.iastate.edu9090/popeye/Wiki.jsp?p
ageAcademic.Basic.CV.Publication
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 3746.
  • 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 (BIDM06).
    191-195.

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.

39
  • Thanks!

40
SLM example
Package
Package Hierarchy

Scope Limitation
A schedule ontology
Visible there is an activity
Hidden details of the activity
CTS06 Paper a.k.a 1
41
DL Interpretation - Example
42
Messages
y
y
T1
T2
C?
C(y)
y
y
T1
T2
C
43
Tableau Expansion
Tableau Expansion for ALCPC with acyclic concept
importing
More expressive extensions in action SHOIQ P
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