1 Object-Orientation in Ontology Date: April 30, 2007 Byunggul Koh Taeksu Kim.
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Transcript of 1 Object-Orientation in Ontology Date: April 30, 2007 Byunggul Koh Taeksu Kim.
1
Object-Orientation in Ontology
Date: April 30, 2007
Byunggul KohTaeksu Kim
2
Contents
Ontology Overview Definition Elements of Ontology Semantic Web Consumer products
Ontology Language RDF RDF Schema Object Oriented Features in RDF OWL Object Oriented Features in OWL
References & Appendix
3
Semantics
Semantic
Symbol Object
Person can recognize the object by semantics
木
Tree
나무
4weak semanticsweak semantics
strong semanticsstrong semantics
Is Disjoint Subclass of with transitivity property
Logical Theory
Thesaurus Has Narrower Meaning Than
TaxonomyIs Sub-Classification of
Conceptual Model Is Subclass of
DB Schemas, XML Schema
First Order Logic
RelationalModel, XML
OWL
RDF/S
Semantic Expressivity
5
Logical Theory
Thesaurus Has Narrower Meaning Than
TaxonomyIs Sub-Classification of
Conceptual Model Is Subclass of
Is Disjoint Subclass of with transitivity property
weak semanticsweak semantics
strong semanticsstrong semantics
ER
Semantic Expressivity
Problem: Very GeneralSemantic Expressivity: Very High
Problem: Local Semantic Expressivity: Low
Problem: GeneralSemantic Expressivity: Medium
Problem: Local Semantic Expressivity: High
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Definition of ontology
In computer science
Represents a set of concepts within a domainRepresents a set of concepts within a domain
Relationships between those conceptsRelationships between those concepts
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Elements of an ontology (1/3)
Class Relationship
Properties
It need to specify descriptions for the following kinds of concepts:
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Elements of an ontology (2/3)
Classes Is abstract groups, sets, or collections of objects May contain individuals, other classes, or a
combination of both
Property Objects can be described by assigning attributes
to them Has a name and a value, Is used to store information that is specific to the
object
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Elements of an ontology (3/3)
Relationship Property is to describe the relationships
between objects Relation is an property whose value is another
object Ex: Successor: Ford Explorer
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Ontology Language
OWL
•Developed as a follow-on from RDF and RDFS, as well as earlier ontology language projects including OIL, DAML and DAML+OIL.
KIF•Syntax for first-order logic that is based on S-expressions
CycL
•First-order predicate calculus with some higher-order extensions
Is a formal language used to encode the ontology
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Usage of an ontology
Tomorrow's applications can be "intelligent" in the sense that they can more accurately work
at the human conceptual level
Has many applying area
Ubiquitous Computing
InformationIntegration
A.I.Semantic Web
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Example of Using ontology
.251.25SquareXAB035
.751.5
RoundXAB023
…Price ($US)
Size (in)ShapeCatalog No.
.4531S550298
.3537R550296
…Price ($US)
Diam (mm)
Geom.Part No.
Washer
Catalog No.Shape Size Price
iMetal Corp.
E-Machina
iMetal Corp.
E-Machina
Manufacturer
.451.25Square550298
.351.5Round550296
.751.5RoundXAB023
.251.25SquareXAB035
…Price ($US)Size (in)ShapeMfr No.
Supplier ASupplier
B
Buyer
Ontology
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Applying area of ontology Semantic web
Way of enabling the semantics to be used by web applications and intelligent agents
Standard W3C
RDF DAML-OIL OWL
ISO/IEC Topic maps
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Elements of a semantic web
HigherHigherSemanticsSemantics
SemanticsSemantics
Structure Structure & Syntax& Syntax
Logical Layer - Formal semantic - Reasoning support - Heavyweight ontologies
Schema Layer - Definition of vocabulary - Lightweight ontologies
Data Layer - Simple data model and Syntax for metadata - RDF: Instances
OWL
RDF Schema
RDF
XML Schema
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Layer of Elements
HigherHigherSemanticsSemantics
SemanticsSemantics
Structure Structure & Syntax& Syntax
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Semantic Web Scenario 1
Feature
Reconstruction
Issue instanceHistoricevent
Site
has
hasreconstructs
Pertains to
Instance of
http://dlib.etc.ucla.edu/Forum/Curia
http://dlib.etc.ucla.edu/Forum
Reconstructionissue
Roof construction
http://dlib.etc.ucla.edu/issue/roof
http://tes.htm
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Semantic Web Scenario 2
Arch of Forum
Curia Iulia
North sectorof Forumdescribes
describes
includes
includespotentially describes
Page1http://test1.html
Page2http://test2.html
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Contents
Ontology Overview Definition Elements of Ontology Semantic Web Consumer products
Ontology Language RDF RDF Schema Object Oriented Features in RDF OWL Object Oriented Features in OWL
References & Appendix
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About metadataFind Things in the Real World
Library Video shop Phone book
• Author• Title
• Subject• ISDN
• …
Book’s location
•Actor’s name• Director’s name
• Genre• …
Video’s name
• Name• Location
• …
Phone number of Pizzahut
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About metadata Common Thread in Find Things
Based on metadata Information about information
E.g. Finding information
Book’s location Using information about information
Book’s title, author, etc.
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About metadata Searching in WWW
The Web is a lot like a really big library
There is hardly any metadata on the Web
Search engine do the equivalent of going through the library, reading every book, and allowing us to look things up based on the words in the text.
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Introduction to RDF
Resource Description Framework
Is W3C standard for encoding knowledge, for the web
A framework for supporting resource description, or metadata
Make the management and navigation of Web data easier
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RDF Triple
Subject Predicate Object
Article(http://bluewater.tistory.com/16) Authored_by
Byunggul Koh
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Graph representation of RDF
Byunggul Kohhttp://bluewater.tistory.com/16Authored_by
http://bluewater.tistory.com/16 http://bluewater.tistory.com
Byunggul Koh Korea
Authored_by
Name nationality
Subject ObjectPredicate
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RDF vs. XML
RDF XML
Semantics Syntax
Graph Tree
Relation representationData representation
Simple syntax
Great Scalability Lack of scalability
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Serialization Syntaxes: RDF/XML
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Serialization Syntaxes: Notation 3
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Application
RDF Site Summary (RSS)
Publishing information about updates of a web page
RDF Site Summary (RSS 1.0) Based on RDF
Really Simple Syndication (RSS 2.0) Based on XML & XML Schema
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Application
RDF Site Summary (RSS)
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RDF Schema
RDF specification Extensible knowledge representation
language intended to structure RDF resources
Provides basic elements for the description of ontology
Called RDF vocabularies
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Example of RDF Schema
eg:Document eg:author eg:Person
http://example.com/Proposal/
Byunggul KohInformation Management-A Proposal
eg:author
eg:nameeg:title
rdfs:Resource
rdf:Property
rdfs:type
rdfs:subClassOfrdfs:subClassOf
rdfs:domain rdfs:range
rdf:type rdf:type
rdfs:subClassOf
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Object-Oriented Features in RDF (1/4)
rdfs:Resource All things described by RDF are called resources
rdfs:Class Declare a resource as a class for other resources
rdf:Property The class of RDF properties
rdfs:subClassOf Declare hierarchies of classes
rdfs:subPropertyOf State that all resources related by one property are also
related by another
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Object-Oriented Features in RDF (2/4)
rdf:type State that a resource is an instance of a class
rdfs:domain Declares the class of the subject in a triple
using this property as predicate P rdfs:domain C
rdfs:range Declares the values of a property are instances
of one or more classes P rdfs:range C
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Object-Oriented Features in RDF (3/4)
Person
Teacher
teacher
rdfs:domain
<rdfs:Class rdf:ID="Person"> <rdfs:subClassOf rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Resource"/></rdfs:Class>
<rdfs:Class rdf:ID="Teacher"> <rdfs:subClassOf rdf:resource="#Person"/></rdfs:Class> <rdf:Property rdf:ID="teacher"> <rdfs:domain rdf:resource="#Course"/> <rdfs:range rdf:resource="#Teacher"/></rdf:Property>
rdf:Property
Course
rdfs:range
rdfs:subClassOf
rdfs:subClassOf
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Object-Oriented Features in RDF (4/4)
Classes in RDF Class
Associations in RDF Attributes in RDF
Property
Instances in RDF Type
RDF has sufficient features for Object-Oriented paradigm
Appendix
36
Contents
Ontology Overview Definition Elements of Ontology Semantic Web Consumer products
Ontology Language RDF RDF Schema Object Oriented Features in RDF OWL Object Oriented Features in OWL
References & Appendix
37
What is OWL?
Web Ontology Language Built on top of RDF OWL is
Stronger language with greater machine interpretability than RDF
Greater vocabulary and stronger syntax than RDF
E.g. Inverse, Union, Intersection
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Three Sublanguages
OWL Lite
OWL DL OWL Full
• Classification hierarchy • Simple constraint features
• Maximum expressiveness and the syntactic freedom • No computational guarantees
• Maximum expressiveness without losing computational completeness
Appendix
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Object-Oriented Features in OWL (1/8)
owl:Class Class is a group of individuals that belong together
because they share some properties
Individual Individuals are instances of classes
rdfs:subClassOf Class hierarchies may be created by making one or
more statements that a class is a subclass of another class
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Object-Oriented Features in OWL (2/8)
Wine
PortableLiquid
<owl:Class rdf:ID="Wine"> <rdfs:subClassOf rdf:resource="PotableLiquid"/> <rdfs:label xml:lang="en">wine</rdfs:label> <rdfs:label xml:lang="fr">vin</rdfs:label> ... </owl:Class>
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Object-Oriented Features in OWL (3/8)
owl:ObjectProperty, owl:DatatypeProperty Datatype properties
Relations between instances of classes and RDF literals and XML Schema datatypes
Object properties Relations between instances of two classes.
rdf:Property rdfs:subPropertyOf
Property hierarchies may be created by making one or more statements that a property is a subproperty of one or more other properties
rdfs:domain A domain of a property limits the individuals to which the
property can be applied rdfs:range
The range of a property limits the individuals that the property may have as its value
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Object-Oriented Features in OWL (4/8)
<owl:ObjectProperty rdf:ID="hasColor"> <rdfs:subPropertyOf rdf:resource="#hasWineDescriptor"/> <rdfs:range rdf:resource="#WineColor" /> ...</owl:ObjectProperty>
Wine
WineDescriptorPortableLiquid
WineColor
hasWineDescriptor
hasColor
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Object-Oriented Features in OWL (5/8)
owl:equivalentClass Two classes may be stated to be equivalent
owl:equivalentProperty Two properties may be stated to be equivalent
owl:sameAs Two individuals may be stated to be the same
owl:differentFrom An individual may be stated to be different from other
individuals owl:intersectionOf
Intersections of named classes and restrictions owl:unionOf
Arbitrary Boolean combinations of classes and restrictions
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Object-Oriented Features in OWL (6/8)
<owl:Class rdf:ID=“Vehicle"> <owl:equivalentClass rdf:resource=“Car"/></owl:Class>
<Wine rdf:ID="MikesFavoriteWine"> <owl:sameAs rdf:resource="#StGenevieveTexasWhite" /> </Wine>
Vechicle
Car
Equus
owl:equivalentClass
rdf:type
Wine
StGenevieveTexasWhiteMikesFavoriteWine
rdf:typerdf:type
Same instances
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Object-Oriented Features in OWL (7/8)
<owl:Class rdf:ID="WhiteBurgundy"> <owl:intersectionOf rdf:parseType="Collection"> <owl:Class rdf:about="#Burgundy" /> <owl:Class rdf:about="#WhiteWine" /> </owl:intersectionOf> </owl:Class>
White WineBurgundy
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Object-Oriented Features in OWL (8/8)
<owl:Class rdf:ID="Fruit"> <owl:unionOf rdf:parseType="Collection"> <owl:Class rdf:about="#SweetFruit" /> <owl:Class rdf:about="#NonSweetFruit" /> </owl:unionOf></owl:Class>
NonSweetFruitSweetFruit
Appendix
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Expression Power of OWL
OWL model can express The disjoint of two classes The intersection and complement of two classes Minimum and maximum cardinality of the class Symmetric, transitive, functional, and inverse-functional
property of the class Inverse relation of two property Create equivalent classes which has different name
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Contents
Ontology Overview Definition Elements of Ontology Semantic Web Consumer products
Ontology Language RDF RDF Schema Object Oriented Features in RDF OWL Object Oriented Features in OWL
References & Appendix
49
References
W3C, A Semantic Web Primer for Object-Oriented Software Developers, available at http://www.w3.org/TR/sw-oosd-primer/, 2006
Asuncion Gomez-Perez et al., "Ontological Engineering," Springer, 2004
OWL Web Ontology Language Use Cases and Requirements, http://www.w3.org/TR/webont-req/
OWL Web Ontology Language Overview, http://www.w3.org/TR/owl-features/
RDF Primer, http://www.w3.org/TR/rdf-primer/ Ontology, Wikipedia Overview of Ontology, SNU IDB Lab., 2006 Overview of RDF, SNU IDB Lab., 2006
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Appendix
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RDFS (1/3)
rdfs:Resource rdfs:Class rdfs:Literal
The class of literal values such as strings and integers
rdfs:Datatype rdfs:Datatype is the class of datatypes
rdf:XMLLiteral The class of XML literal values
rdf:Property
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RDFS (2/3)
rdfs:range rdfs:domain rdf:type rdfs:subClassOf rdfs:subPropertyOf rdfs:label
Instance of rdf:Property that may be used to provide a human-readable version of a resource's name
rdfs:comment Instance of rdf:Property that may be used to provide a
human-readable description of a resource
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RDFS (3/3) rdfs:Container rdf:Bag rdf:Seq rdf:Alt rdfs:ContainerMembershipProperty rdfs:member rdf:List rdf:first rdf:rest rdf:nil rdf:Statement rdf:subject rdf:predicate rdf:object rdfs:seeAlso rdfs:isDefinedBy rdf:value Back to p.34
54
OWL (1/3)
owl:AllDifferent A number of individuals may be stated to be mutually
distinct in one AllDifferent statement owl:inverseOf
If the property P1 is stated to be the inverse of the property P2, P1(x,y) iff P2(y,x)
owl:allValuesFrom If an instance of the class is related by the property to a
second individual, then the second individual can be inferred to be an instance of the local range restriction class
owl:someValuesFrom A particular class may have a restriction on a property that
at least one value for that property is of a certain type
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OWL (2/3)
owl:cardinality Cardinality is provided as a convenience when it is
useful to state that a property on a class has both minCardinality 0 and maxCardinality 0 or both minCardinality 1 and maxCardinality 1
owl:minCardinality If a minCardinality of 1 is stated on a property with
respect to a class, then any instance of that class will be related to at least one individual by that property
owl:maxCardinality If a maxCardinality of 1 is stated on a property with
respect to a class, then any instance of that class will be related to at most one individual by that property
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OWL (3/3)
owl:one of Classes can be described by enumeration of the
individuals that make up the class
owl:hasValue A property can be required to have a certain individual
as a value
owl:disjointWith Classes may be stated to be disjoint from each other
owl:unionOf owl:intersectionOf owl:complementOf
Back to p.45
57
OWL Lite, OWL DL, OWL Full
OWL Lite OWL DL OWL Full
Following property can not be specified owl:minCardinality owl:maxCardinality owl:cardinality
Only 0 or 1 can be used
owl:hasValue owl:disjointWith owl:oneOf owl:complementOf owl:unionOf
Following property can not be specified FunctionalProperty InverseFunctionalProperty owl:cardinality
Can not use metaclassCan not import the OWL Full ontology
All features in specification can be used
NCA IV- RER-04059: A Research on Web Ontology Development Guideline, National Information Society Agency, 2004. 12
Back to p.37