towards collaborative environments for ontology construction and sharing

CTS 2006 Las Vegas, USA. May 15, 2006 1

Iowa State University Department of Computer ScienceArtificial Intelligence Research Laboratory

Towards Collaborative Environments for Ontology Construction and Sharing

Jie Bao, Doina Caragea and Vasant Honavar

Artificial Intelligence Research LaboratoryComputer Science Department

Iowa State University, Ames, IA USA 50011Email: {baojie, dcaragea, honavar}@cs.iastate.edu

May 15, 2006



Outline

• Motivation

• Package-based Description Logics: Language Features

• Package-based Description Logics : Semantics

• Collaborative Ontology Building Tools



Challenges in Ontology Building

• Collaboration Challenges– Integration of local points of view– Avoiding inconsistencies and unintended coupling– Selective knowledge hiding– Partial ontology reuse

• Scaleability Challenges– Editing– Storage– Reasoning



Local vs Global Semantics

• Ontologies represent local views of its producers – Biologist: dog species only eats animal

Ontology: Dog is Carnivore and all Carnivore only eats Animal

– Pet owner: pet dog sometimes eats DogFood, which is not animalOntology: PetDog is Dog and some PetDog eats DogFood; DogFood is CannedFood and not Animal

• Global semantics could lead to conflicts

• Localizing knowledge is helpful to reduce such risks



Partial vs All-or-Nothing Reuse

General Pet

Poultry Livestock

Animal Ontology(Centralized)

MyPet

General

Pet

Poultry

Livestock

MyPet

Animal Ontology(Package-extended)

Semantic importing

Semantics incorporated in MyPet ontology

Semantics not presented in MyPet ontologyLegend:

• Lack of modularity: all or nothing – Eg: how to import part

of the animal ontology?

• Modular ontologies : more flexible partial reuse– Less communication – Less memory– Less parsing time.– Less unwanted junk!



Organizational vs Semantic Structure

Animal

is a part of

• Organizational structure: how to arrange terms for better usage and understanding– Eg: Computer Science Dictionary and

Biology Dictionary

• Semantic structure: how to relate meanings of terms– Eg: ‘Mouse’ is a kind of ‘Animal’ or

‘Mouse’ is part of ‘Computer’



Knowledge Hiding vs Sharing

• Ontology reflects shared knowledge in general

Locally visible:Has date

Globally visible:Has activity

Bob’ schedule ontology

• However, the provider may also wish to hide part of it. – Privacy, Copyright, Security

• Partial hiding helps for safer ontology organization– Reduce unexpected coupling

– Separate “details” and “interface”



Ontology Languages Today

• Description Logics(DL), OWL, OBO (life science ontologies)

• However, the state of art in ontology languages is reminiscent of the early programming languages

– Uncontrolled use of global terms – Unwanted and uncontrolled interactions between fragments

– Difficult to reuse: all or nothing



Ontology Languages Needed

• Modularity– Has localized terminology and semantics– Allows partial ontology reuse– Utilizes organizational and semantic structure – Enables collaborative and scaleable tools

• Knowledge Hiding– Builds safer ontologies– Reduces unwanted interactions– Hides details (encapsulate semantics)



Outline

• Motivation


• Package-based Description Logics: Semantics




P-DL

P3

protected

1. Whole ontology consists of a set of packages

2. Packages are organized in hierarchies

3. Terms and axioms are defined in packages with scope limitations

P1

P2

public

private

P1

P2

public

private



Package• A package is an ontology

module with clearly defined access interface;

• Each package is defined with certain ontology language and – Import: terms from other

packages– Interface: terms visible to other

packages

• Each term has a home package

1. Whole ontology consists of a set of packages

General Pet

Poultry Livestock

Animal ontology

Hound, PointerPet

DogGeneral

P3

protected

P1

P2

public

private

P1

P2

public

private



Nested Package • A nested package is part of

another package– Super package, sub package– Form a package hierarchy

• Could be used to represent the organizational structure– Arrange knowledge– Enforce hierarchical

management of knowledge

2. Packages are organized in hierarchies

General

Pet

Dog

Animal ontology

P3

protected

P1

P2

public

private

P1

P2

public

private



Scope Limitation Modifier • Defines the visible scope of a term or

axiom• SLM of an ontology term or axiom t

– is a boolean function V(t,r), where r is a package

– Package r could access t iff V(t,r) = True.

• Example SLMs– Public (t,r): t is accessible from anywhere– Private (t,r): t is only available in the home

package– Protected(t,r): t is accessible from the

home package and its recursive sub packages.

3. Terms has scope limitation

P3

protected

P1

P2

public

private

P1

P2

public

private

P3

protected

P1

P2

public

private

P1

P2

public

private



SLM: example(TBC)A schedule ontology

Hidden: details of the activity

Visible: there is an activity

Hidden semantics may still be used in reasoning



Outline

• Motivation






Local Interpretation

Carnivore IP

AnimalIP

ΔIP

eatsIPgoofyIP

Ontology: Carnivore AnimalInterpretation: In any world that conforms to the

ontology, for any instance x of Carnivore, x is also an instance of Animal.



Local and Global Interpretations

AnimalI

CarnivoreI

DogI

I

PetDogI

goofyI

PetI

eatsI

g

g

g

g

g

g

g

fooIg

DogFoodI g

AnimalI

CarnivoreI

DogI

goofyI fooI

DogI

PetIPetDogI

plutoI

eatsI

1

1

1

1

2

2

2

2

2

2

DogFoodI 2

AnimalI2

=



Distributed Interpretation

• Global interpretations may not exist for all packages

• Distributed interpretations may still exist for selected sets of packages.

A BC D

1B CC P

2B,C

B C

3

B,C=

x x’

BI2 = CI2 =PI2 AI1 = BI1,CI1 =DI1

=x x’

BI3

y

AI1 = BI1

CI1= DI1

y’

CI3

P1,P3

P1,P2



Outline

• Motivation

• Package-based Description Logics : Language Features


• Collaborative Ontology Building



Collaborative Ontology Building

Ontology modularity facilitates collaborative building

• Each package can be independently developed• Different curators can concurrently edit the

ontology on different packages• Ontology can be only partially loaded• Unwanted interactions are minimized by limiting

term and axiom visibility• Module access privileges can be controlled by

the package hierarchy



The INDUS DAG EditorThe COB Editor



Summary

• Collaborative ontology building calls for modular ontology representation.

• Package-based description logics (P-DL) offers an ontology language for modularity and selective knowledge sharing.

• Efficient collaborative ontology building tools can be realized with P-DL.

Ongoing Work• Reasoning algorithm• Extension to OWL



Backup



Ontology Languages Today (2)

• Distributed Description Logics (DDL)– Allows “bridge rules” between

concepts across ontology modules

• E-Connections– Connects DL modules with

special types of roles called “links”

PetOwner

Petowns

• Limitations– Expressivity– Semantic Soundness

PetAnimal

Goldfish

(onto)

(into)



Interpretation of Importing

• Domain relations are compositional consistent: r13=r12

O r23

– Therefore domain relations are transitively reusable.

x x’

ΔI1 ΔI2

CI1 CI2

r12

ΔI3

r13 r23

x’’CI3

• Domain relation: individual correspondence between local domains

• Importing establishes one-to-one domain relations between local domains– “Copied” individuals are shared between

local domains– Ensure exact reasoning w.r.t. the

integrated ontology



AnimalI

CarnivoreI

DogI

goofyI

fooI

DogI

PetIPetDogI

plutoI

eatsI

(a) (b)

1

1

1

12

2

2

2

2

2

DogFoodI 2

AnimalI2

Local Interpretation

• Semantics of foreign terms is not imported

• One term may have different local interpretations

towards collaborative environments for ontology construction and sharing

Technology

ontology languages

ontology term

package package r

ontology construction

ontology module

p goofy i p

p animal

package super package