ontologies: introduction, design, languages and tools

Ontologies

Fulvio Corno, Laura FarinettiPolitecnico di TorinoDipartimento di Automatica e Informaticae-Lite Research Group – http://elite.polito.it

F. Corno, L. Farinetti- Politecnico di Torino 2

SummaryIntroduction to ontologiesOntology “engineering”

ontologies creation processOntology languagesTools for ontologies design

Semantically rich descriptions to support search

http://dictybase.org/db/html/help/GO.htmlhttp://dictybase.org/db/html/help/GO.html

Topic ={metabolism, …}

OntologiesAn ontology is an explicit description of a domain

conceptsproperties and attributes of conceptsconstraints on properties and attributesindividuals (often, but not always)

An ontology defines a common vocabularya shared understanding

“Ontology engineering”Defining terms in the domain and relations among them

defining concepts in the domain (classes)arranging the concepts in a hierarchy(subclass-superclass hierarchy)defining which attributes and properties (slots) classes can have and constraints on their valuesdefining individuals and filling in slot values

Why develop an ontology?

To share common understanding of the structure of information

among peopleamong software agents

To enable reuse of domain knowledgeto avoid “re-inventing the wheel”to introduce standards to allow interoperability

An ontology

Certificate

Diploma

2 years

1 year

Is_equivalent_to

A more complex ontology[base.Entity]

Person Worker

Faculty Professor

AssistantProfessorAssociateProfessorFullProfessorVisitingProfessor

Lecturer PostDoc

Assistant ResearchAssistantTeachingAssistant

AdministrativeStaffDirector Chair {Professor} Dean {Professor} ClericalStaffSystemsStaff

Student UndergraduateStudentGraduateStudent

A more complex ontologyOrganization

Department School University Program ResearchGroupInstitute

Publication Article

TechnicalReportJournalArticleConferencePaper

UnofficialPublicationBook Software Manual Specification

Work Course Research

Schedule

A more complex ontology

Relation Argument 1 Argument 2 ======================================================publicationAuthor Publication Person publicationDate Publication .DATE publicationResearch Publication Research softwareVersion Software .STRING softwareDocumentation Software Publication teacherOf Faculty Course teachingAssistantOf TeachingAssistant Course takesCourse Student Course age Person .NUMBER emailAddress Person .STRING head Organization PersonundergraduateDegreeFrom Person UniversitymastersDegreeFrom Person UniversitydoctoralDegreeFrom Person University advisor Student Professor subOrganization Organization Organization ………..

Example of ontology engineering

chairchair

1.A piece of furniture consisting of a seat, legs, back, and oftenarms, designed to accommodate one person.2.A seat of office, authority, or dignity, such as that of a bishop.

a.An office or position of authority, such as a professorship.b.A person who holds an office or a position of authority, such as one who presides over a meeting or administers a department of instruction at a college; a chairperson.

3.The position of a player in an orchestra.4.Slang. The electric chair.5.A seat carried about on poles; a sedan chair.6.Any of several devices that serve to support or secure, such as a metal block that supports and holds railroad track in position.

chairchair

A piece of furniture consisting of a seat, legs, back, and often arms, designed to accommodate one person.

chairchair

chairchair seatseat stoolstool benchbench

Something I can sit on

??????

“sittable”“sittable”

tabletable

“for_sitting”“for_sitting”

tabletable

Something designed for sitting

Ontology structure

tabletable

Ingredients

Conceptsshorthand name (internal use)synthetic title (to be displayed)definition (real unambiguous shared definition)

Relationships among conceptsis_aother

Annotations

Concepts

Some piece of furniture that can be used to sit on, either by design or by its shape.

Furniture to sit on

Shorthand name

Synthetic title

Definition“sittable”“sittable”

Internationalization

Furniture to sit on

Shorthand name

Synthetic title

Definition

Furniture to sit onFurniture to sit onFurniture to sit onFurniture to sit onFurniture to sit onFurniture to sit on

Relationships

tabletable

is_a is_a is_ais_a

roomroommaterialmaterial

woodwood

classroomclassroom

dining roomdining room

is_ais_a

Relationships

tabletable

is_a is_a is_ais_a

roomroommaterialmaterial

woodwood

classroomclassroom

dining roomdining room

is_ais_a

made_of

furnished

made_of

Ontology building blocksOntologies generally describe:

Individualsthe basic or “ground level” objects

Classessets, collections, or types of objects

Attributesproperties, features, characteristics, or parameters that objects can have and share

Relationshipsways that objects can be related to one another

Individuals

Also known as “instances”can be concrete objects

animalsmoleculestrees

or abstract objectsnumberswords

ConceptsAlso known as “Classes”

abstract groups, sets, or collections of objectsThey may contain

individualsother classesa combination of both

ExamplesPerson: the class of all peopleVehicle: the class of all vehicles

ConceptsCan be defined extensionally …

By defining every object that falls under the definition of the conceptA class C is extensionally defined if and only if for every class C', if C' has exactly the same members of C, C and C' are identicalE.g.: DayOfWeek = {Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday}

… or intensionallyBy defining the necessary and sufficient conditions for belonging to the conceptE.g.: “bachelor” is an “unmarried man”

Concepts

Defined by Name: any identifier, usually carefully chosenDefinition: describes the well agreed meaning of the concept, in a human readable formTerms (Lexicon): list of terms (synonyms, etc.) usually adopted to identify the concept

SubsumptionA concept (class) can subsume / be subsumed by any other classSubsumption is used to establish class hierarchies

Class partitionA set of related classes and associated rules that allow objects to be placed into the appropriate class

GEOMETRICFIGURE

GEOMETRICPOINT

GEOMETRICPOINT TWO

DIMENSIONALFIGURE

TWODIMENSIONAL

FIGUREONE

DIMENSIONALFIGURE

ONEDIMENSIONAL

FIGURE

Class partitionDisjoint partition

A disjoint partition rule guarantees that a single instance of a class cannot be in more than one sub-classes E.g. one specific truckcannot be in both 4-axle and6-axle classes

VEHICLEVEHICLE

CARCARTRUCKTRUCK

6-AXLE6-AXLE 4-AXLE4-AXLE

Class partition

Exhaustive partitionevery concrete object in the super-class is an instance of at least one of the partition classes

Attributes

Describe specific featuresCan be complex (e.g.: list of values)Defined for a class/concept (e.g. car)Examples:

number-of-doors: 4number-of-wheels: 4engine: {3.0L,4.0L}

Relationships

Attributes that relate two or more concepts two concepts → binary relationshipthree concepts → ternary relationship

Domainthe concept(s) from which the relationship departs

Rangethe concept(s) to which the relationship applies

Relationships

ExamplesCar(MiniMinor) → individual definitionCar(Mini) → individual definitionSuccessor(Mini,MiniMinor) → relationship

domain range

Commonly used relationshipsSubsumption

the most importantis-superclass-ofusually denoted by its inverse is-a(is-subclass-of)

Meronymyis-part-ofdescribes how object are combined together to form composite objects

Example

http://www.yeastgenome.org/help/GO.htmlhttp://www.yeastgenome.org/help/GO.html

http://www.webology.ir/2006/v3n3/a28.htmlhttp://www.webology.ir/2006/v3n3/a28.html

Ontology alignment

Ontology languages

RDF / RDF Schema

RDF Schema example

RDFS problemsRDFS is too “weak” to describe resources with a suitable level of details

range and domain cannot be localized (e.g. the range of hasChild is a person when applied to a person, elephant when applied to an elephant)no constraints on existence or cardinality (e.g. all instances of persons have one and only one mother which is a person, and have exactly two parents)

RDFS problemsit is not possible to define transitive, inverseor symmetrical statements (e.g. part of is a transitive property, hasPart is the inverse of isPartOf, touches is symmetrical)

Reasoning is not well supportedNon standard semantics, no native reasonerexists

Requirements for an ontology language

Extend existing Web standardsXML, RDF, RDFS, ...

Easy to understand and to usebased on well known KR languages

Formally specifiedAdequate expressive powerAutomatic support for reasoning

Stack of Web languages

XOL SHOE OML RDF(S)

DAML+OILbioinformatics communitybioinformatics community

University of MarylandUniversity of Maryland

University of WashingtonUniversity of Washington

IST EU project OntoKnowledgeIST EU project OntoKnowledge

W3CW3C

DARPADARPA

Ontology Web Language (OWL)4th level on the semantic web cakeBuilt on top of

XMLRDF/S

Three versionsLiteDL (maps to Description Logic)Full (not fully tractable)

Serializable as XML

Ontology Web Language (OWL)

OWL-DLBased on Description LogicWell defined formal semantics

well defined rules to treat sentence meaningwell defined assumptions on the world being modeled

Well known reasoning/inferencingalgorithms

tractable, conclusions can be derived in finite time

Widely available reasoning systems

Building blocks in OWLOntology declaration (XML syntax)

Ontology metadata (information about the ontology)

<rdf:RDF xmlns:owl =http://www.w3.org/2002/07/owl#" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#"xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:xsd ="http://www.w3.org/2001/XMLSchema#">

<owl:Ontology rdf:about=""><rdfs:comment>An example OWL ontology</rdfs:comment><owl:priorVersion

rdf:resource="http://www.mydomain.org/uni-ns-old"/><owl:imports

rdf:resource="http://www.mydomain.org/persons"/><rdfs:label>University Ontology</rdfs:label>

</owl:Ontology>

<owl:Ontology rdf:about=""><rdfs:comment>An example OWL ontology</rdfs:comment><owl:priorVersion

rdf:resource="http://www.mydomain.org/uni-ns-old"/><owl:imports

rdf:resource="http://www.mydomain.org/persons"/><rdfs:label>University Ontology</rdfs:label>

</owl:Ontology>

ClassesEvery class is a descendant of

owl:ThingClasses are defined using

owl:Class

Equivalenceowl:equivalentClass

<owl:Class rdf:ID="Vehicle"/><owl:Class rdf:ID="Vehicle"/>

<owl:Class rdf:ID="Car"><owl:equivalentClass rdf:resource="#Automobile"/>

</owl:Class>

<owl:Class rdf:ID="Car"><owl:equivalentClass rdf:resource="#Automobile"/>

</owl:Class>

Subsumption

Provided byowl:subClassOf

<owl:Class rdf:ID="2-Wheel-Drive"><rdfs:subClassOf rdf:resource="#Car"/>

</owl:Class>

<owl:Class rdf:ID="2-Wheel-Drive"><rdfs:subClassOf rdf:resource="#Car"/>

</owl:Class>

Partitions

Disjoint partitionowl:disjointWith

<owl:Class rdf:about="#2-Wheel-Drive"><owl:disjointWith

rdf:resource="#4-Wheel-Drive"/></owl:Class>

<owl:Class rdf:about="#2-Wheel-Drive"><owl:disjointWith

rdf:resource="#4-Wheel-Drive"/></owl:Class>

Partitions

Exhaustive partitionowl:oneOf

<owl:Class rdf:ID="Car"><owl:oneOf rdf:parseType="Collection">

<owl:Thing rdf:about="#2-Wheel-Drive"/><owl:Thing rdf:about="#4-Wheel-Drive"/>

</owl:oneOf></owl:Class>

<owl:Class rdf:ID="Car"><owl:oneOf rdf:parseType="Collection">

<owl:Thing rdf:about="#2-Wheel-Drive"/><owl:Thing rdf:about="#4-Wheel-Drive"/>

AttributesKnown also as “properties”Datatype properties

Attributes that specify a class features by means of data (XSD datatype)Phone, title, age

Object propertiesAttributes that define relationships between classes (Relations)isTaughtBy(Class(course), Class(professor))

Datatype propertiesAllow to describe a specific aspect of a concept

Based on XSD data typesThe range specifies the data typeThe domain specifies the class to which the property is referred

<owl:DatatypeProperty rdf:ID="age"><rdfs:domain rdf:resource="#Person"/><rdfs:range rdf:resource="http://www.w3.org/2001/

XMLSchema#nonNegativeInteger"/></owl:DatatypeProperty>

<owl:DatatypeProperty rdf:ID="age"><rdfs:domain rdf:resource="#Person"/><rdfs:range rdf:resource="http://www.w3.org/2001/

XMLSchema#nonNegativeInteger"/></owl:DatatypeProperty>

Relationships

Directed From one concept to another, no viceversa

Defined through object propertiesDomain: the class(es) from which the relation departsRange: the relation destination(s)

Subsumption between relationships is possible

Relationships

Example

<owl:ObjectProperty rdf:ID="isTaughtBy"><rdfs:domain rdf:resource="#course"/><rdfs:range rdf:resource="#academicStaffMember"/><rdfs:subPropertyOf rdf:resource="#involves"/>

</owl:ObjectProperty>

<owl:ObjectProperty rdf:ID="isTaughtBy"><rdfs:domain rdf:resource="#course"/><rdfs:range rdf:resource="#academicStaffMember"/><rdfs:subPropertyOf rdf:resource="#involves"/>

Instances (individuals)No unique name assumption in OWL

If two instances have a different name or ID this does not imply that they are different individualsE.g.: “Queen Elizabeth”, “The Queen” and “Elizabeth Windsor” might all refer to the same individual It must be explicitly stated that individuals are the same as each other, or different to each other

Instances (individuals)Defined by means of

rdf:Description + rdf:Type

39</uni:age>

</academicStaffMember><rdf:Description rdf:ID="949353">

<rdf:type rdf:resource="#academicStaffMember"/></rdf:Description>

39</uni:age>

</academicStaffMember><rdf:Description rdf:ID="949353">

<rdf:type rdf:resource="#academicStaffMember"/></rdf:Description>

Advanced constructsOWL supports several advanced constructs to define classes and relationshipsIntensional definition of classes

By defining constraints on attribute values (either object or datatype properties)

<owl:Class rdf:about="#academicStaffMember"><rdfs:subClassOf>

<owl:Restriction><owl:onProperty rdf:resource="#teaches"/><owl:someValuesFrom

rdf:resource="#undergraduateCourse"/></owl:Restriction>

</rdfs:subClassOf></owl:Class>

<owl:Class rdf:about="#academicStaffMember"><rdfs:subClassOf>

<owl:Restriction><owl:onProperty rdf:resource="#teaches"/><owl:someValuesFrom

rdf:resource="#undergraduateCourse"/></owl:Restriction>

</rdfs:subClassOf></owl:Class>

Advanced constructsCardinality

Used to fix the number of instances that can be relatedE.g.: a department should have at least 10 members

<owl:Class rdf:about="#department"><rdfs:subClassOf>

<owl:Restriction><owl:onProperty rdf:resource="#hasMember"/><owl:minCardinality

rdf:datatype="&xsd;nonNegativeInteger"> 10</owl:minCardinality>

</owl:Restriction></rdfs:subClassOf></owl:Class>

<owl:Class rdf:about="#department"><rdfs:subClassOf>

<owl:Restriction><owl:onProperty rdf:resource="#hasMember"/><owl:minCardinality

rdf:datatype="&xsd;nonNegativeInteger"> 10</owl:minCardinality>

</owl:Restriction></rdfs:subClassOf></owl:Class>

Special propertiesowl:TransitiveProperty

defines a transitive property, such as “has better grade than”, “is taller than”, or “is ancestor of”

owl:SymmetricPropertydefines a symmetric property, such as “has same grade as” or “is sibling of”

owl:FunctionalPropertydefines a property that has at most one value for each object, such as “age”, “height”, or “directSupervisor”

Special properties

owl:InverseFunctionalPropertydefines a property for which two different objects cannot have the same valueE.g.: the property “isTheSocialSecurityNumberFor”: a social security number is assigned to one person only

OWL class constructors

OWL axioms

OWL: what for?To build an ontology

define classes and provide information on themdefine properties and provide information on them

To express facts about a domainprovide information on instances (individuals)

To reason about ontologies and factsdiscover consequences of what is expressly stated

Example of ontology building in OWL with Protégé

Protégé

Open source ontology editor Developed by Stanford Center for Biomedical Informatics Research at the Stanford University School of Medicinehttp://protege.stanford.edu/

Project steps

0. Conceptual design of the ontology1. Classes definition2. Properties definition3. Individuals definition4. Restrictions definition

Step 0

Conceptual design of the ontology

AccommodationAccommodation

BudgetAccommodation

Bed&BreakfastBed&Breakfast

HotelHotel

CampingCamping

AccommodationRating

ContactContact

DestinationDestination

FamilyDestination

QuietDestination

BeachBeach

BackpackerDestination

ActivityActivity

AdventureAdventure

RelaxationRelaxation

SightseeingSightseeing

SportsSports

MuseumsMuseumsSafariSafari

BunjeeJumpingBunjeeJumping

SunbathingSunbathing

YogaYoga

HikingHiking

SurfingSurfing

OneStarRatingOneStarRating

TwoStarRatingTwoStarRating

ThreeStarRatingThreeStarRating

RiminiRiminiBardonecchiaBardonecchia

CapreraCaprera

GallipoliGallipoli

SheratonSheraton

Luxury HotelLuxury Hotel

string

hasRating

hasAccommodation

hasContact

hasActivity

isOffered

hasZipCode

hasEMail

hasStreet

hasCity

Step 1a

Define classes and subclassesIs-a relationship, or subsumption

AccommodationRating

ContactContact

ActivityActivity

BudgetAccommodation

HotelHotel

CampingCamping

FamilyDestination

QuietDestination

BeachBeach

BackpackerDestinationHikingHiking

SurfingSurfing

SunbathingSunbathing

YogaYoga

SafariSafariBunjeeJumpingBunjeeJumping

MuseumsMuseums

AdventureAdventure

SportsSports

<owl:Class rdf:ID="Camping"><rdfs:subClassOf><owl:Class rdf:ID="Accommodation"/>

</rdfs:subClassOf></owl:Class><owl:Class rdf:ID="BudgetAccommodation"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class><owl:Class rdf:ID="BedAndBreakfast"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class><owl:Class rdf:ID="LuxuryHotel"><rdfs:subClassOf><owl:Class rdf:ID="Hotel"/>

</rdfs:subClassOf></owl:Class><owl:Class rdf:about="#Hotel"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class>

<owl:Class rdf:ID="Camping"><rdfs:subClassOf><owl:Class rdf:ID="Accommodation"/>

</rdfs:subClassOf></owl:Class><owl:Class rdf:ID="BudgetAccommodation"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class><owl:Class rdf:ID="BedAndBreakfast"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class><owl:Class rdf:ID="LuxuryHotel"><rdfs:subClassOf><owl:Class rdf:ID="Hotel"/>

</rdfs:subClassOf></owl:Class><owl:Class rdf:about="#Hotel"><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class>

OWL code

Step 1b

Define disjointclasses AccommodationAccommodation

BudgetAccommodation

HotelHotel

CampingCamping

Disjoint

<owl:Class rdf:about="#Hotel"><owl:disjointWith rdf:resource="#Camping"/><owl:disjointWith><owl:Class rdf:about="#BedAndBreakfast"/>

</owl:disjointWith><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class>

<owl:Class rdf:about="#Hotel"><owl:disjointWith rdf:resource="#Camping"/><owl:disjointWith><owl:Class rdf:about="#BedAndBreakfast"/>

</owl:disjointWith><rdfs:subClassOf rdf:resource="#Accommodation"/>

</owl:Class>

Step 1c

Define multipleinheritance

ActivityActivity

AdventureAdventure SightseeingSightseeing

MuseumsMuseumsSafariSafari

BunjeeJumpingBunjeeJumping

Step 2a

Define object propertiesrelationships

hasAccommodation

Domain

<owl:ObjectProperty rdf:ID="hasAccommodation"><rdfs:domain rdf:resource="#Destination"/><rdfs:range rdf:resource="#Accommodation"/>

Step 2bDefine object properties characteristics

E.g: define an inverse object property

ActivityActivity

hasActivity

isOffered

<owl:ObjectProperty rdf:about="#isOffered"><rdfs:range rdf:resource="#Destination"/><owl:inverseOf rdf:resource="#hasActivity"/><rdfs:domain rdf:resource="#Activity"/>

Step 2c

Define datatype propertiesThe range specifies thedata type

<owl:DatatypeProperty rdf:ID="hasEMail"><rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/><rdfs:domain rdf:resource="#Contact"/>

</owl:DatatypeProperty><owl:DatatypeProperty rdf:ID="hasZipCode"><rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#int"/><rdfs:domain rdf:resource="#Contact"/>

</owl:DatatypeProperty>

<owl:DatatypeProperty rdf:ID="hasEMail"><rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/><rdfs:domain rdf:resource="#Contact"/>

</owl:DatatypeProperty><owl:DatatypeProperty rdf:ID="hasZipCode"><rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#int"/><rdfs:domain rdf:resource="#Contact"/>

</owl:DatatypeProperty>

ContactContact

string

hasZipCode

hasEMail

hasStreet

Step 3

Define individualsinstances

AccommodationRating

FamilyDestination

RiminiRiminiBardonecchiaBardonecchia

Step 4

Define restrictionsTo restrict the individuals that belong to a classQuantifier restrictions (existential, universal quantifiers)Cardinality restrictionshasValue restrictions

Step 4 – example 1

FamilyDestination is a Destination with at least one accommodation and at least 2 activities

Cardinality restriction

Necessary andsufficient condition

FamilyDestination

ActivityActivity

hasAccommodation >= 1

hasActivity >= 2

Step 4 – example 1<owl:Class rdf:ID="FamilyDestination">

<owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Restriction><owl:onProperty><owl:ObjectProperty rdf:ID="hasAccommodation"/>

</owl:onProperty><owl:minCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#int">1</owl:minCardinality>

</owl:Restriction><owl:Restriction><owl:minCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#int">2</owl:minCardinality><owl:onProperty><owl:ObjectProperty rdf:ID="hasActivity"/>

</owl:onProperty></owl:Restriction><owl:Class rdf:about="#Destination"/>

</owl:intersectionOf></owl:Class>

</owl:equivalentClass></owl:Class>

<owl:Class rdf:ID="FamilyDestination"><owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Restriction><owl:onProperty><owl:ObjectProperty rdf:ID="hasAccommodation"/>

</owl:onProperty><owl:minCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#int">1</owl:minCardinality>

</owl:Restriction><owl:Restriction><owl:minCardinality rdf:datatype="http://www.w3.org/2001/XMLSchema#int">2</owl:minCardinality><owl:onProperty><owl:ObjectProperty rdf:ID="hasActivity"/>

</owl:onProperty></owl:Restriction><owl:Class rdf:about="#Destination"/>

FamilyDestination is a Destination with at least one accommodation and at least 2 activities

QuietDestination is a Destination that is not chosen by noisy families

Complement restriction

FamilyDestination

QuietDestination

<owl:Class rdf:ID="QuietDestination"><owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Class>

<owl:complementOf rdf:resource="#FamilyDestination"/></owl:Class><owl:Class rdf:about="#Destination"/>

<owl:Class rdf:ID="QuietDestination"><owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Class>

<owl:complementOf rdf:resource="#FamilyDestination"/></owl:Class><owl:Class rdf:about="#Destination"/>

QuietDestination is a Destination that is not chosen by noisy families

BudgetAccommodation is an Accommodation that has either one or two star rating

BudgetAccommodation

HotelHotel

CampingCamping

AccommodationRating

SheratonSheraton

hasRating

Existential restriction

Step 4 – example 3<owl:Class rdf:ID="BudgetAccommodation"><owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Restriction>

<owl:onProperty><owl:ObjectProperty rdf:ID="hasRating"/>

</owl:onProperty><owl:someValuesFrom><owl:Class>

<owl:oneOf rdf:parseType="Collection"><AccommodationRating rdf:ID="OneStarRating"/><AccommodationRating rdf:ID="TwoStarRating"/>

</owl:someValuesFrom></owl:Restriction><owl:Class rdf:about="#Accommodation"/>

<owl:Class rdf:ID="BudgetAccommodation"><owl:equivalentClass><owl:Class><owl:intersectionOf rdf:parseType="Collection"><owl:Restriction>

<owl:onProperty><owl:ObjectProperty rdf:ID="hasRating"/>

</owl:onProperty><owl:someValuesFrom><owl:Class>

<owl:oneOf rdf:parseType="Collection"><AccommodationRating rdf:ID="OneStarRating"/><AccommodationRating rdf:ID="TwoStarRating"/>

</owl:someValuesFrom></owl:Restriction><owl:Class rdf:about="#Accommodation"/>

BudgetAccommodation is an Accommodation that has either one or two star rating

Step 4 – example 4BackpackerDestination is a Destination that provides budget accommodation and offers sport or adventure activities

BudgetAccommodation

ActivityActivity

AdventureAdventure

SportsSports

hasAccommodation

hasActivity

Bed&BreakfastBed&BreakfastHotelHotel

CampingCamping

Step 4 – example 4<owl:Class rdf:ID="BackpackerDestination">

<owl:equivalentClass><owl:Class>

<owl:intersectionOf rdf:parseType="Collection"><owl:Restriction>

<owl:onProperty><owl:ObjectProperty rdf:ID="hasAccommodation"/>

</owl:onProperty><owl:someValuesFrom rdf:resource="#BudgetAccommodation"/>

</owl:Restriction><owl:Class rdf:about="#Destination"/><owl:Restriction>

<owl:onProperty><owl:ObjectProperty rdf:ID="hasActivity"/>

</owl:onProperty><owl:someValuesFrom>

<owl:Class><owl:unionOf rdf:parseType="Collection">

<owl:Class rdf:about="#Sports"/><owl:Class rdf:about="#Adventure"/>

</owl:unionOf></owl:Class>

</owl:someValuesFrom></owl:Restriction>

<owl:Class rdf:ID="BackpackerDestination"><owl:equivalentClass>

<owl:Class><owl:intersectionOf rdf:parseType="Collection">

<owl:Restriction><owl:onProperty>

<owl:ObjectProperty rdf:ID="hasAccommodation"/></owl:onProperty><owl:someValuesFrom rdf:resource="#BudgetAccommodation"/>

</owl:Restriction><owl:Class rdf:about="#Destination"/><owl:Restriction>

<owl:onProperty><owl:ObjectProperty rdf:ID="hasActivity"/>

</owl:onProperty><owl:someValuesFrom>

<owl:Class><owl:unionOf rdf:parseType="Collection">

<owl:Class rdf:about="#Sports"/><owl:Class rdf:about="#Adventure"/>

</owl:unionOf></owl:Class>

</owl:someValuesFrom></owl:Restriction>

BackpackerDestination is a Destination that provides budget accommodation and offers sport or adventure activities

Semantic annotation

Explicit representation of a factA given resource......is related to......a given conceptual representation

Annotation

xxxyxyxyyx xyxyx xyxyxyx xyxyyx yyxyyx

yxyyyx yxxyyx xyyx yxyyyxyx

xyxyyxxy xyx xyyxyx

xyyx xyx yyyxyxyxyyyxyxyyx xyyxyyx

xyxyyx yxy xyyxyx

URIURI Content

TextXML / XHTMLMultimedia

Structured documentsFragment

xxxyxyxyyx xyxyx xyxyxyx xyxyyx yyxyyx

xyxyyxxy xyx xyyxyx

xyxyyx yxy xyyxyx

Resource = fragment

xyxyxyyx xyxyx xyxyxyx xyxyyx yyxyyx

xyxyyxxy xyx xyyxyx

xyxyyx yxy xyyxyx

StructureXML nestingXHTML sectioningDIV nesting

Visual appearanceLayout reverse-engineeringExploit common usability conventionsDiscard navigation information

Pushing fragmentation to the end

Annotate each sentence, or each wordIn this way, we interpret semantics as linguistic semantics (deep semantics)The rest of this presentation favors the interpretation of conceptual semantics(shallow semantics)

“…to a given conceptual representation”

Identify a suitable conceptual representation of the resourceIs a single concept a suitable representation?

Weighted relationshipsConceptual spectraFuzzy logic…

“…is related to…”

Annotation storageAnnotation creationRDF (ResourceDescriptionFramework)

related xxxxyyxyx

Explicit annotation

This is the DREAM of the Semantic WebEach resource is explicitly (manually?) annotated

by the authorby an independent “classifier”

Annotation may refer to different ontologies, and may relate to the resource or to [some of] its fragments

see the Linked Data projectF. Corno, L. Farinetti- Politecnico di Torino 101

Automatic annotation

Given a set of resourcesGiven an ontologyGenerate a set of annotations, describing the resources with respect to the ontology concepts

Also called “Information Extraction”

Automatic annotation creation

Can a concept “know” if a resource is relevant?

The concept name is not relevantThe documents may be in other languages

Bootstrap problem!Need “syntactical” ties with conceptsNeed “semantic” knowledge with resources

Bootstrap techniques

Provide a set of words / patterns / sequences / rules / … for each concept (and for each language) that “activate” the conceptProvide a set of relevant “real” resourcesclassified on the ontology concepts…depends on the classification algorithm

Annotation for multimedia

Semantic engines don’t care about resource format (text, video, image, ...)Automatic annotation is well developed and robust for text, only

Text extraction, whenever possible (even if partially)Multimodal approaches to enrich knowledgeUse user experience (Web 2.0)

License

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