a semantic importing approach to knowledge reuse from multiple ontologies

July 25,2007, AAAI 2007, Vancouver, British Columbia, Canada . Research supported by NSF IIS-0639230 1/21

Iowa State University Department of Computer ScienceArtificial Intelligence Research Laboratory

A Semantic Importing Approach to Knowledge Reuse from Multiple Ontologies

Jie Bao, Giora Slutzki and Vasant Honavar

Artificial Intelligence Research LaboratoryComputer Science Department

Iowa State University Ames, IA USA 50011

Email: {baojie,slutzki,honavar}@cs.iastate.eduwww.cild.iastate.edu



Outline

• Part I: Modular Ontologies– Motivation– Desiderata

• Part II: Package-based Description Logics (P-DL)– Syntax– Semantics– Properties

• Part III: Discussions and Summary– Related Work & Conclusions



From Web Pages to Ontologies

• Web: Network effect

[Diagram: Joanne Luciano, Predictive Medicine; Drug discovery demo using RDF, Sideran Seamark and Oracle 10g]

• Web pages: web Ontologies : semantic web



Description Logics

• Basic elements: concepts and roles • Basic DL: ALC

– ⊔ (disjunction): Child = Boy ⊔ Girl– ⊓ (conjunction): Mother = Female ⊓ Parent (existential restriction): Parent =

hasChild.Human (value restriction): Human ⊑ hasBrother.Man (negation): Boy ⊑ Girl

• Many extensions: nominals, transitive roles, …• OWL-DL corresponds to DL SHOIN(D)



Ontology Reuse in OWL: Syntactic Importing

• ontology reuse by owl:import• owl:import = copy-and-paste

owl:imports



Analogy: Paper Writing in OWL fashion

Recent development in modular ontologies…

In this paper, we present two algorithms A and B to …

(Alice, 2001)

(Bob, 2007)


In this paper, we extend the algorithm A proposed by (Alice,2001) …

copy+paste

• no partial reuse• loss of context



Modular Ontology Language Desiderata

• Support partial reuse• Support preservation of context• Provide “sufficient” modeling ability• Avoid known problems in existing proposals

– Lack of support for transitive reuse of knowledge– Non-preservation of concept unsatisfiability



Desired properties not supported by existing approaches

• Preservation of Unsatisfiability

• Transitive Reusability

vv BullDog Animal ?

Dog Pet⊑ Pet ⊑ Animal

O1 O2 O3

Bird ⊑ FlyNonFly=1Fl

yO1 O2

Penguin ⊑ BirdPenguin ⊑

NonFly

Bird ⊓ NonFly

unsat

Penguin

Unsat?

Dog PetBullDog Dog⊑



Outline






P-DL: Semantic Importing• Each module is called a package• A package can reuse a subset of names defined in other packages

O1 (Animal) O2 (Pet)



P-DL: Importing akin to Citation

1:Dog 1:Animal⊑1:Cat 1:Animal⊑

P1

P2

2:PetOwner ⊑2:owns.1:Dog



P-DL: Contextualized Negation

Black, White

1 White = Black

2 White = Black ⊔ Red

1 = White ⊔Black

2 = White ⊔ Black ⊔ Red



Semantics of P-DL

• Domain relations are compositionally consistent: r13 = r23 O r12

• More requirements are needed when importing of roles and nominals is allowed.

x x’

ΔI1 ΔI2

1:DogI11:DogI2

r12

ΔI3

r13 r23

x’’1:DogI3

• Each package has a local interpretation

• Importing establishes domain relations – Partial

– One-to-one

– Directional

• (1:Dog)I2 =r12(1:DogI1)



P-DL Supports

• The preservation of unsatisfiability

• Transitive Reusability

vvBullDog Animal

Dog ⊑ Pet Pet ⊑ Animal

P1 P2 P3

Bird ⊑ FlyNonFly=1Fl

yP1 P2

Penguin ⊑ BirdPenguin ⊑

NonFly

Bird ⊓ NonFly

unsat

Bird ⊓ NonFly

unsatBirdNonFly

Dog PetBullDog Dog⊑



Modeling Ability of P-DL

• Inter-module concept inclusion: – 1:Dog 2:Pet⊑

• Inter-module role inclusion: – 1:brotherOf 2:siblingOf⊑

• Use roles to “link” concepts: – 2:DogOwner (⊑ 2:owns.1:Dog)

• Use of foreign roles and foreign nominals



Outline






Modular Ontology Languages

CЄ (SHOIN(D))

OWL

1998 2002 2003 2004 2005 2006 2007

C-OWLC-OWLCTXML

E-Connections

P-DL

DDL(Distributed DL)DFOL

DDL with Role Concept

Mapping

CЄ(SHIF(D))IHN+s

DL ALCPC SHOIQP



Comparison

Contextualized Semantics

Preservation of Unsatisfiability

Transitive Reusability

Decidability

OWL-DL No Yes Yes Yes

DDL Yes No No Yes (bridge rule between

concepts),

Open (bridge rules between

roles)

E-Connections Yes N.A. No Yes

P-DL Yes Yes Yes Yes



Comparison

1,4 Limited Support 2,3 May be simulated using syntactical encoding

C

C

C

CC

C

C

C

P

P

P

P

P

P

P

x

P-DL



Summary

• P-DL supports– Semantic importing – akin to citation– Selective reuse– Contextualized interpretation– Preservation of concept unsatisfiability– Transitive reuse of knowledge– A broad range of modeling scenarios

P-DL offers – an alternative semantics for owl:imports



Ongoing Work

• Distributed reasoning algorithm – Developed for P-DL ALCPC and SHIQP

– Implementation underway based on Pellet DL reasoner

• ABox Modularity

Thanks!

• More questions? Poster @ 6pm• Acknowledgement: George Voutsadakis



Backup



Implicit Context

“Sheep are black”“Scotland at this time there is at least one cow that appears to be black on at least one side”“Some of the sheep in Scotland are black”

Picture courtesy of http://shinyblacksheep.com/



Distributed, Modular Ontologies

Distributed ontology modules• Are produced by autonomous participants

– Are limited in their scope – Represent different points of view

• Lack global semantics– Need contextualized semantics

• Need selective or partial knowledge reuse • Need distributed inference algorithms without forcing

ontology integration• Should facilitate network effect



Analogy: Paper Writing


In this paper, we present two algorithms A and B to …

(Alice, 2001)

(Bob, 2007)

Combining Ontologies

Ontology Modularization


In this paper, we extend the algorithm A proposed by (Alice,2001) …

Same global domain: modular ontologies Multiple independent participants

Possible (partial) reuseContextualized Semantics

Citation is not copy+paste, hence does not result in a single, combined document



Desideratum: Contextualized Semantics

People Work

O1 O2

“those that are not male are female”

“companies hire people”



Desideratum: Directionality

vvD EvvA B

vvA B

vvD EX



Desideratum: Monotonicity and Transitive Reuse

Dogvv

vvDog Animal

Pet Animalvv

O1 O2 O3



Desideratum: Distributed Inference

vv

Integrated ontology Modular ontology

Dog Animal vvDog Animal



A Very Very Short DL Primer

• Description Logics (DL): – a knowledge representation

formalism to describe ontologies

– the foundation for web ontology languages, e.g., OWL

• Ontology example– A Dog is an Animal

– A Dog eats some DogFood

– goofy is a Dog

concept

role

individual

axioms



Semantics of P-DL

Cardinality closure of roles



P-DL Families

• P – package extension with importing of any type of names (concept, role and nominal)– P- - acyclic importing: if P (directly or indirectly) imports Q, then Q

cannot (directly or indirectly) import P– PC – importing of concept names only

• Examples: – ALCPC

[Bao et al,CRR 2006] – ALCPC

-[Bao et al,WI 2006] – SHIQP[Bao et al,ISWC 2007]

– SHOIQP[Bao et al,AAAI 2007]



Two General Approaches for Modularity

Modular Ontology Languages

Design Pattern

Preserve context by

Interpreting axioms in local domains

Requiring explicit declaration of context; disallow axioms that might be used of context

Semantics Contextualized First-order

Example Example: DDL, E-Connections, P-DL

Conservative Extension [Grau et al 2007]

Pros Support distributed reasoning, stronger modeling ability

Compatible to existing tools

Cons Need to extend existing reasoners

No known distributed reasoning support; restrictive language usage; context may not always be aware of



DDL and E-connections vs P-DL• P-DL can simulate

– DDL with bridge rules using subsumption between • imported concepts and local concepts • imported roles and local roles

– (one-way binary) E-Connections using roles that relate a local concept with an imported concept

• DDL, E-Connection or their combination cannot simulate P-DL– One-to-one domain relations cannot be simulated by DDL or E-

Connections– P-DL, unlike DDL and E-connections, supports transitive reuse of

knowledge



Distributed Reasoning with P-DL

• Tableau algorithms reported for ALCPC and SHIQP

What is a “Dog”?

“Dog” is a type of “Animal”

Dog

Dog ⊑ AnimalP2 P1



P-DL: Importing akin to Citation

• Semantic importing akin to “citation”

• Package 2 cites package 1 for the definition of ‘1:Dog’– Interpretation of ‘1:Dog’ is the same on the “shared” portions of the

local domains of packages 1 and 2– The two packages need not agree on the interpretation of other

unrelated concepts (e.g., Cats)

• P-DL supports selective knowledge reuse

P1 P2

1:Dog 2:PetDog 1:Dogvv

a semantic importing approach to knowledge reuse from multiple ontologies

Education

semantics of p

modeling ability of

summary pdlsupports

cowl ctxml econnections

dog pet pet animal o

transitive roles

ontologies web

dog use of foreign roles