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Divide and Conquer Semantic Web with Modular Ontologies - A Brief Review of Modular Ontology Language Formalisms Jie Bao and Vasant Honavar Artificial Intelligence Research Laboratory, Department of Computer Science, Iowa State University, Ames, IA 50011-1040, USA.

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Divide and Conquer Semantic Web with Modular Ontologies - A Brief Review of Modular Ontology Language Formalisms


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slide1

Divide and Conquer Semantic Web with ModularOntologies - A Brief Review of Modular OntologyLanguage Formalisms

Jie Baoand Vasant Honavar

Artificial Intelligence Research Laboratory,

Department of Computer Science,

Iowa State University,

Ames, IA 50011-1040, USA.

{baojie, honavar}@cs.iastate.edu

First International Workshop on Modular Ontologies (WoMo2006),

co-located with ISWC 2006

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 1

outline
Outline
  • Why Modular Ontology
  • Evolution of Modular Ontologies
  • Local Domain disjointness
  • Conclusion

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 2

local points of view
Local Points of View

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 3

messy spaghetti ontologies
Messy “Spaghetti” Ontologies

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 4

when load a large ontology
When load a large ontology…

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 5

so we may need
So we may need

An ontology language that has the support for

  • Localized semantics
  • Fine-grained organization.
  • Partial use/reuse

Some more desirable features

  • Collaborative ontology building.
  • Distributed reasoning

In short: a modular ontology language

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 6

outline7
Outline
  • Why Modular Ontology
  • Evolution of Modular Ontologies
  • Local Domain disjointness
  • Conclusion

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 7

timeline
Timeline

1998 2002 2003 2004 2005 2006

CTXML

C-OWL

DFOL

DDL

Role<->Concept

Mapping

P-DL

OWL

?

(One purpose of the workshop)

CЄ(SHOIN(D))

E-Connections

CЄ(SHIF(D))

IHN+s

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 8

pre semantic web 1
Pre Semantic Web (1)
  • Cyc micro-theory [Lenat. Commun. ACM,1995]
    • The collections of concepts and facts pertaining to particular knowledge domains
  • Partition based Logics [Amir & McIlraith. KR 2000]
    • automatically decompose propositional and first-order logic (FOL) into partitions
    • an algorithm for reasoning with such partitions using message passing.

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 9

pre semantic web 2
Pre Semantic Web (2)
  • Local Model Semantics [Giunchiglia & Ghidini. KR 1998]
  • Distributed First-Order Logic [Ghidini & Serafini. 1998]

Locality +

Compatibility

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 10

slide11
DDL
  • Distributed Description Logics [Borgida & Serafini CoopIS 2002]
  • Syntax: CTXML [Bouquet etal. MeaN 2002], C-OWL [Bouquet et al. ISWC 2003]
  • Extensions: Role-concept mapping [Ghidini & Serafini, ESWC 2006], role-role mapping [Ghidini & Serafini, WOMO 2006]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 11

e connections
E-connections
  • E-connections [Kutz etal. KR 2002] [Grau et al. ISWC 2004] [Grau, Dissertation 2005]
  • More role constructors
  • Generalized link [Parsia & Grau, AAAI 2005]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 12

slide13
P-DL
  • Package-based Description Logics [Bao et al, CTS 2006, ASWC 2006, ISWC 2006]
    • An importing approach

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 13

more recent proposals
More Recent Proposals
  • Semantic Importing [Pan etal. WOMO 2006]
    • Allow both syntatical importing (owl:imports) and semantic importing (owl:semanticImports)
  • Local Ontologies [Grau etal, KR 2006] [Grau & Horrocks IJCAI 2007]
    • Restrict axioms to be “local”, i.e., has no global effect, i.e. no axiom should define “T”(top)
    • Local ontologies are conservative extension to each other (i.e. no new knowledge over old module):
      • O1 U O2 |= a <-> O2 |= a (a is a formula in O2)

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 14

outline15
Outline
  • Why Modular Ontology
  • Evolution of Modular Ontologies
  • Local Domain disjointness
  • Conclusion

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 15

disjoint local domains
Disjoint Local Domains
  • Implicit domain disjointness – DDL
    • domain relations do not indicate individual identity
    • even if two individuals 1 : x and 2 : x are the same object, they are still treated as if they are different individuals
  • Explicit domain disjointness – E-Connections
    • "The general idea behind E-Connections is that the interpretation domains of the connected knowledge bases (…) are kept disjoint and interconnected by means of link relations…” [Grau, 2005]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 16

domain relations

Δ

Δ

friendOf

neighbourOf

r13

r13

1

3

Domain Relations

Disjoint local domains (DDL and E-connections)

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 17

ddl subsumption propagation problem
DDL :Subsumption Propagation Problem

DDL domain relations are not transitively reusable (without extra restrictions)

Cm1

Dm2

C into D

C into E ?

D into E

Em3

[Grau, 2005]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 18

ddl inter module unsatisfiability problem
DDL Inter-module Unsatisfiability Problem

Flym1

Bird onto Penguin

Penguinm2

Birdm1

~Fly onto Penguin

[Grau, 2005]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 19

slide20
Why?
  • Bridge rules can be seen as special roles
  • For a role to simulate subsumption, it should preserve some properties of subsumption
    • e.g. Transitive (globally reusable) , non-empty, transfer (un)satisfability
    • Arbitrary bridge rule semantics leads to problems
    • Better to prevent those problems with a more normative semantics

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 20

e connections expressiveness problems
E-Connections: Expressiveness Problems
  • A class cannot be declared in an ontology as a subclass of a foreign class;
  • A property cannot be declared as sub-relation of a foreign property;
  • An individual cannot be declared as an instance of a foreign class
  • A pair of individuals cannot instantiate a foreign property;
  • The combined use of E-Connections and owl:imports raises a number of difficulties.

[Grau, Dissertation 2005]

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 21

p dl partially overlapped domains

r12

P-DL: Partially Overlapped Domains

ΔI1

ΔI2

x’

x

CI2

CI1

x

r13

r23

CI

x’’

CI3

Global model obtained from local

models by merging shared individuals

ΔI3

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 22

why partially overlapped
Why Partially Overlapped ?
  • Ensure a term is always explained the same across multiple modules
    • Does not mean the loss of local point of view
    • “I know what your means, but I still don’t agree with you”
  • Ensure reasoning exactness
    • Satisfability transfer: “copies of possible things are also possible”
  • Ensure knowledge is transitively reusable
    • “Since everybody knows Apple has only one meaning, we can use it regardless where you hear it from”

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 23

why partially overlapped 2
Why Partially Overlapped ? (2)
  • Reasoning support
    • Possible for very expressive P-DL: SHIQP
      • Nominals “O” may also be allowed (nominals are in the shared local domain).
    • Allows federated reasoning:
      • Peer reasoners with access only to local knowledge
      • Global knowledge discovered via messages
  • Compatible to OWL syntax
    • Only needs to redefine owl:imports
    • Maximal tool backwards compatibility

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 24

outline25
Outline
  • Why Modular Ontology
  • Evolution of Modular Ontologies
  • Local Domain disjointness
  • Conclusion

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 25

modular ontologies today
Modular Ontologies Today
  • Has several approaches to support localized semantics
  • Several syntax extensions to OWL
  • Tools available for limited reasoning and editing supports: DRAGO, Pellet, Swoop, COB-Editor
  • Several methods to decompose large ontologies into modules.

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 26

open problems
Open Problems
  • What modular ontologies are safe and robustly decidable?
  • Complexity of expressive modular ontologies.
  • A community-wide accepted, OWL-compatible syntax for expressive modular ontologies.
  • Highly optimized, truly distributed reasoner
    • optimized on caching, parallel searching, reasoning on grid
    • Integration with p2p systems
  • Collaborative ontology building with modularity.

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 27

slide28
Thanks!

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 28

miserable life in ontology eng
Miserable Life in Ontology Eng.
  • OpenCyc, only a small portion of the Cyc KB, needs 9 hours to load into Protégé.
  • Protege crashes when I try to open Wordnet ontology.
  • I really wants to reuse Grape knowledge in the Food ontology, but can not do it without accepting all other “junk” in the it.
  • My ontology is small, but a reasoning request is unbelievably slow, just because it imports one big ontology
  • When I submit a single-word change to the Gene ontology, the GO CVS duplicates the entire ontology.
    • And it is overwritten by somebody the next day!

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 29

happy life in software eng
Happy Life in Software Eng.
  • Highly organized program structure
  • Mature methods to build large programs
  • Scalable building, debugging, running of applications
  • Collaborative software building by modules
  • Controllable interactions between modules.

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 30

se was miserable too
SE was miserable, too
  • Until fine-grained organization is introduced:

Semantic structure

Organizational structure

WoMo 2006 @ ISWC, Athens, GA USA. Nov 5, 2006 31