Ontologies: introduction, design, languages and tools

Ontologies

Fulvio Corno, Laura Farinetti
Politecnico di Torino
Dipartimento di Automatica e Informatica
e-Lite Research Group – http://elite.polito.it

Summary
Introduction to ontologies
Ontology “engineering”
ontologies creation process
Ontology languages
Tools for ontologies design

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

Semantically rich descriptions to
support search
http://dictybase.org/db/html/help/GO.html
http://dictybase.org/db/html/help/GO.html

Topic =
{metabolism, …}


Ontologies
An ontology is an explicit description of
a domain
concepts
properties and attributes of concepts
constraints on properties and attributes
individuals (often, but not always)
An ontology defines
a common vocabulary
a 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
values
defining individuals and filling in slot values

Why develop an ontology?
To share common understanding of the
structure of information
among people
among software agents
To enable reuse of domain knowledge
to avoid “re-inventing the wheel”
to introduce standards to allow interoperability


An ontology
takes Certificate
1 year
Is_a
Is_equivalent_to
takes
Is_a
HNC Award

Is_a Is_a
takes
HND
2 years Diploma
takes

A more complex ontology
[base.Entity]
Person
Worker
Faculty
Professor
AssistantProfessor
AssociateProfessor
FullProfessor
VisitingProfessor
Lecturer
PostDoc
Assistant
ResearchAssistant
TeachingAssistant
AdministrativeStaff
Director
Chair {Professor}
Dean {Professor}
ClericalStaff
SystemsStaff
Student
UndergraduateStudent
GraduateStudent

Organization
Department
School
University
Program
ResearchGroup
Institute
Publication
Article
TechnicalReport
JournalArticle
ConferencePaper
UnofficialPublication
Book
Software
Manual
Specification
Work
Course
Research
Schedule


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 Person
undergraduateDegreeFrom Person University
mastersDegreeFrom Person University
doctoralDegreeFrom Person University
advisor Student Professor
subOrganization Organization Organization ………..


Example of ontology engineering

chair


1.A piece of furniture consisting of a seat, legs, back, and often
arms, 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.

chair



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

chair



chair seat stool bench



Something I can sit on

???





“sittable”





“sittable”

table




“sittable”

Something designed for sitting

“for_sitting”

table



Ontology structure

“sittable”

“for_sitting”

table



Ingredients
Concepts
shorthand name (internal use)
synthetic title (to be displayed)
definition (real unambiguous shared definition)
Relationships among concepts
is_a
other
Annotations

Concepts
Synthetic title
Furniture to sit on

“sittable” Definition
Shorthand name Some piece of furniture that
can be used to sit on, either by
design or by its shape.


Internationalization
Synthetic title
Furniture to sit on
Furniture to sit on
Furniture to sit on
Furniture to sit on
Furniture to sit on
Furniture to sit on
Furniture to sit on
“sittable” Definition
Shorthand name Some piece of furniture that
Some piece of furniture that
Some piece of furniture that
can Somepieceofoffurniturethat
Some piece sitfurniture that
canbe used totositon, eitherthat
Some pieceof on, eitherby
canbe used totositfurniture that
Some piece of furniture by
canbe used shape. either by
on,
designbe used tosit on, either by
can be by its shape. either by
or used tosit on, either by
design be by its shape. either by
designor used tosit on,
can or used sit on,
designbe by its shape.
can
designor by its shape.
or by its


Relationships
material
room
is_a
is_a
“sittable”
is_a wood
classroom is_a

dining room “for_sitting” is_a
is_a table
is_a is_a is_a


Relationships
made_of
material
room
is_a

furnish
is_a
“sittable”
is_a wood
classroom ed is_a
made_of
dining room “for_sitting” is_a
is_a table
is_a is_a is_a


Ontology building blocks
Ontologies generally describe:
Individuals
the basic or “ground level” objects
Classes
sets, collections, or types of objects
Attributes
properties, features, characteristics, or parameters
that objects can have and share
Relationships
ways that objects can be related to one another

Individuals
Also known as “instances”
can be concrete objects
animals
molecules
trees
or abstract objects
numbers
words


Concepts
Also known as “Classes”
abstract groups, sets, or collections of objects
They may contain
individuals
other classes
a combination of both
Examples
Person: the class of all people
Vehicle: the class of all vehicles

Concepts
Can be defined extensionally …
By defining every object that falls under the definition
of the concept
A 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 identical
E.g.: DayOfWeek = {Monday, Tuesday, Wednesday,
Thursday, Friday, Saturday, Sunday}
… or intensionally
By defining the necessary and sufficient conditions for
belonging to the concept
E.g.: “bachelor” is an “unmarried man”

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


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


Class partition
A set of related classes and associated
rules that allow objects to be placed into
the appropriate class
GEOMETRIC
GEOMETRIC
FIGURE
FIGURE

GEOMETRIC
GEOMETRIC TWO
TWO
POINT
POINT DIMENSIONAL
DIMENSIONAL
FIGURE
FIGURE
ONE
ONE
DIMENSIONAL
DIMENSIONAL
FIGURE
FIGURE


Class partition
Disjoint partition
A disjoint partition rule guarantees that a
single instance of a class cannot be in more
than one sub-classes
VEHICLE
E.g. one specific truck VEHICLE

cannot be in both
4-axle and TRUCK CAR
TRUCK CAR
6-axle classes
6-AXLE 4-AXLE
6-AXLE 4-AXLE


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


Attributes
Describe specific features
Can be complex (e.g.: list of values)
Defined for a class/concept (e.g. car)
Examples:
number-of-doors: 4
number-of-wheels: 4
engine: {3.0L,4.0L}


Relationships
Attributes that relate two or more concepts
two concepts → binary relationship
three concepts → ternary relationship
Domain
the concept(s) from which the relationship
departs
Range
the concept(s) to which the relationship
applies

Relationships
Examples
Car(MiniMinor) → individual definition
Car(Mini) → individual definition
Successor(Mini,MiniMinor) → relationship

domain range


Commonly used relationships
Subsumption
the most important
is-superclass-of
usually denoted by its inverse is-a
(is-subclass-of)
Meronymy
is-part-of
describes how object are combined together
to form composite objects

Example

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

Ontology alignment
http://www.webology.ir/2006/v3n3/a28.html
http://www.webology.ir/2006/v3n3/a28.html


RDF / RDF Schema


RDF Schema example


RDFS problems
RDFS 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 problems
it is not possible to define transitive, inverse
or symmetrical statements (e.g. part of is a
transitive property, hasPart is the inverse of
isPartOf, touches is symmetrical)
Reasoning is not well supported
Non standard semantics, no native reasoner
exists


Requirements for an ontology
language
Extend existing Web standards
XML, RDF, RDFS, ...
Easy to understand and to use
based on well known KR languages
Formally specified
Adequate expressive power
Automatic support for reasoning

Stack of Web languages

W3C
IST EU project
OntoKnowledge OWL
DARPA
bioinformatics
University of OIL
community DAML+OIL
Washington
XOL SHOE OML RDF(S)

University of
XML
Maryland


Ontology Web Language (OWL)
4th level on the semantic web cake
Built on top of
XML
RDF/S
Three versions
Lite
DL (maps to Description Logic)
Full (not fully tractable)
Serializable as XML

Ontology Web Language (OWL)


OWL-DL
Based on Description Logic
Well defined formal semantics
well defined rules to treat sentence meaning
well defined assumptions on the world being
modeled
Well known reasoning/inferencing
algorithms
tractable, conclusions can be derived in finite
time
Widely available reasoning systems

Building blocks in OWL
Ontology declaration (XML syntax)
<rdf:RDF xmlns:owl =http://www.w3.org/2002/07/owl#quot;
<rdf:RDF xmlns:owl =http://www.w3.org/2002/07/owl#quot;
xmlns:rdf =quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;
xmlns:rdf =quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#quot;
xmlns:rdfs=quot;http://www.w3.org/2000/01/rdf-schema#quot;
xmlns:rdfs=quot;http://www.w3.org/2000/01/rdf-schema#quot;
xmlns:xsd =quot;http://www.w3.org/2001/XMLSchema#quot;>
xmlns:xsd =quot;http://www.w3.org/2001/XMLSchema#quot;>

Ontology metadata (information about the
ontology)
<owl:Ontology rdf:about=quot;quot;>
<owl:Ontology rdf:about=quot;quot;>
<rdfs:comment>An example OWL ontology</rdfs:comment>
<rdfs:comment>An example OWL ontology</rdfs:comment>
<owl:priorVersion
<owl:priorVersion
rdf:resource=quot;http://www.mydomain.org/uni-ns-oldquot;/>
rdf:resource=quot;http://www.mydomain.org/uni-ns-oldquot;/>
<owl:imports
<owl:imports
rdf:resource=quot;http://www.mydomain.org/personsquot;/>
rdf:resource=quot;http://www.mydomain.org/personsquot;/>
<rdfs:label>University Ontology</rdfs:label>
<rdfs:label>University Ontology</rdfs:label>
</owl:Ontology>
</owl:Ontology>

Classes
Every class is a descendant of
owl:Thing
Classes are defined using
owl:Class
<owl:Class rdf:ID=quot;Vehiclequot;/>
<owl:Class rdf:ID=quot;Vehiclequot;/>

Equivalence
owl:equivalentClass
<owl:Class rdf:ID=quot;Carquot;>
<owl:equivalentClass rdf:resource=quot;#Automobilequot;/>
<owl:equivalentClass rdf:resource=quot;#Automobilequot;/>
</owl:Class>
</owl:Class>

Subsumption
Provided by
owl:subClassOf

<owl:Class rdf:ID=quot;2-Wheel-Drivequot;>
<owl:Class rdf:ID=quot;2-Wheel-Drivequot;>
<rdfs:subClassOf rdf:resource=quot;#Carquot;/>
<rdfs:subClassOf rdf:resource=quot;#Carquot;/>
</owl:Class>
</owl:Class>


Partitions
Disjoint partition
owl:disjointWith

<owl:Class rdf:about=quot;#2-Wheel-Drivequot;>
<owl:Class rdf:about=quot;#2-Wheel-Drivequot;>
<owl:disjointWith
<owl:disjointWith
rdf:resource=quot;#4-Wheel-Drivequot;/>
rdf:resource=quot;#4-Wheel-Drivequot;/>
</owl:Class>
</owl:Class>


Partitions
Exhaustive partition
owl:oneOf

<owl:oneOf rdf:parseType=quot;Collectionquot;>
<owl:Thing rdf:about=quot;#2-Wheel-Drivequot;/>
</owl:oneOf>
</owl:oneOf>
</owl:Class>
</owl:Class>


Attributes
Known also as “properties”
Datatype properties
Attributes that specify a class features by
means of data (XSD datatype)
Phone, title, age
Object properties
Attributes that define relationships between
classes (Relations)
isTaughtBy(Class(course), Class(professor))


Datatype properties
Allow to describe a specific aspect of a
concept
Based on XSD data types
The range specifies the data type
The domain specifies the class to which the
property is referred
<owl:DatatypeProperty rdf:ID=quot;agequot;>
<owl:DatatypeProperty rdf:ID=quot;agequot;>
<rdfs:domain rdf:resource=quot;#Personquot;/>
<rdfs:domain rdf:resource=quot;#Personquot;/>
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/
XMLSchema#nonNegativeIntegerquot;/>
XMLSchema#nonNegativeIntegerquot;/>
</owl:DatatypeProperty>


Relationships
Directed
From one concept to another, no viceversa
Defined through object properties
Domain: the class(es) from which the relation
departs
Range: the relation destination(s)
Subsumption between relationships is
possible

Relationships
Example
<owl:ObjectProperty rdf:ID=quot;isTaughtByquot;>
<owl:ObjectProperty rdf:ID=quot;isTaughtByquot;>
<rdfs:domain rdf:resource=quot;#coursequot;/>
<rdfs:domain rdf:resource=quot;#coursequot;/>
<rdfs:range rdf:resource=quot;#academicStaffMemberquot;/>
<rdfs:range rdf:resource=quot;#academicStaffMemberquot;/>
<rdfs:subPropertyOf rdf:resource=quot;#involvesquot;/>
<rdfs:subPropertyOf rdf:resource=quot;#involvesquot;/>
</owl:ObjectProperty>


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
individuals
E.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

<academicStaffMember rdf:ID=quot;949352quot;>
<academicStaffMember rdf:ID=quot;949352quot;>
<uni:age rdf:datatype=quot;&xsd;integerquot;>
<uni:age rdf:datatype=quot;&xsd;integerquot;>
39
39
</uni:age>
</uni:age>
</academicStaffMember>
</academicStaffMember>
<rdf:Description rdf:ID=quot;949353quot;>
<rdf:Description rdf:ID=quot;949353quot;>
<rdf:type rdf:resource=quot;#academicStaffMemberquot;/>
<rdf:type rdf:resource=quot;#academicStaffMemberquot;/>
</rdf:Description>
</rdf:Description>


Advanced constructs
OWL supports several advanced constructs to
define classes and relationships
Intensional definition of classes
By defining constraints on attribute values (either
object or datatype properties)
<owl:Class rdf:about=quot;#academicStaffMemberquot;>
<owl:Class rdf:about=quot;#academicStaffMemberquot;>
<rdfs:subClassOf>
<rdfs:subClassOf>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty rdf:resource=quot;#teachesquot;/>
<owl:onProperty rdf:resource=quot;#teachesquot;/>
<owl:someValuesFrom
<owl:someValuesFrom
rdf:resource=quot;#undergraduateCoursequot;/>
rdf:resource=quot;#undergraduateCoursequot;/>
</owl:Restriction>
</owl:Restriction>
</rdfs:subClassOf>
</rdfs:subClassOf>
</owl:Class>
</owl:Class>

Advanced constructs
Cardinality
Used to fix the number of instances that can be
related
E.g.: a department should have at least 10 members

<owl:Class rdf:about=quot;#departmentquot;>
<owl:Class rdf:about=quot;#departmentquot;>
<rdfs:subClassOf>
<rdfs:subClassOf>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty rdf:resource=quot;#hasMemberquot;/>
<owl:onProperty rdf:resource=quot;#hasMemberquot;/>
<owl:minCardinality
<owl:minCardinality
rdf:datatype=quot;&xsd;nonNegativeIntegerquot;> 10
rdf:datatype=quot;&xsd;nonNegativeIntegerquot;> 10
</owl:minCardinality>
</owl:minCardinality>
</owl:Restriction>
</owl:Restriction>
</rdfs:subClassOf>
</rdfs:subClassOf>
</owl:Class>
</owl:Class>


Special properties
owl:TransitiveProperty
defines a transitive property, such as “has better
grade than”, “is taller than”, or “is ancestor of”
owl:SymmetricProperty
defines a symmetric property, such as “has same
grade as” or “is sibling of”
owl:FunctionalProperty
defines a property that has at most one value for
each object, such as “age”, “height”, or
“directSupervisor”


Special properties
owl:InverseFunctionalProperty
defines a property for which two different
objects cannot have the same value
E.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 them
define properties and provide information on
them
To express facts about a domain
provide information on instances (individuals)
To reason about ontologies and facts
discover 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 Medicine
http://protege.stanford.edu/


Project steps
0. Conceptual design of the ontology
1. Classes definition
2. Properties definition
3. Individuals definition
4. Restrictions definition


Step 0
Conceptual design of the ontology


Bed&Breakfast
Bed&Breakfast OneStarRating
OneStarRating
hasRating Accommodation
Accommodation
Rating
Rating
TwoStarRating
TwoStarRating
Accommodation
Accommodation
Camping
Camping
ThreeStarRating
Budget ThreeStarRating
Budget
Accommodation
Accommodation
Hotel
Hotel
int
hasZipCode
hasAccommodation
string
Luxury Hotel
Luxury Hotel
Backpacker Contact
Backpacker Contact
Hiking
Hiking hasStreet
Destination
Destination
Surfing hasEMail
Surfing
string
Sheraton hasContact
Sheraton

Sports isOffered
Sports
Destination
Destination
Beach
Yoga Beach
Yoga
Caprera
Caprera
Activity
Activity
hasCity
hasActivity
Relaxation
Relaxation
Quiet
Quiet string
Destination Family
Destination Family Gallipoli
Gallipoli
Destination
Destination
Sunbathing
Sunbathing
Sightseeing
Adventure Sightseeing
Adventure

Bardonecchia
Bardonecchia
Rimini
Rimini
Safari
Safari
BunjeeJumping
BunjeeJumping Museums
Museums


Step 1a
Define classes and subclasses
Is-a relationship, or subsumption


Bed&Breakfast
Bed&Breakfast
Accommodation
Accommodation
Rating
Rating
Accommodation
Accommodation
Camping
Camping
Budget
Budget
Accommodation
Accommodation
Hotel
Hotel

Luxury Hotel
Luxury Hotel
Backpacker Contact
Backpacker Contact
Hiking
Hiking Destination
Destination
Surfing
Surfing

Sports
Sports
Destination
Destination
Beach
Yoga Beach
Yoga
Activity
Activity

Relaxation
Relaxation
Quiet
Quiet
Destination Family
Destination Family
Destination
Destination
Sunbathing
Sunbathing
Sightseeing
Adventure Sightseeing
Adventure

Safari
Safari
BunjeeJumping
Museums


OWL code
<owl:Class rdf:ID=quot;Campingquot;>
<owl:Class rdf:ID=quot;Campingquot;>
<rdfs:subClassOf>
<rdfs:subClassOf>
<owl:Class rdf:ID=quot;Accommodationquot;/>
<owl:Class rdf:ID=quot;Accommodationquot;/>
</rdfs:subClassOf>
</rdfs:subClassOf>
</owl:Class>
</owl:Class>
<owl:Class rdf:ID=quot;BudgetAccommodationquot;>
<rdfs:subClassOf rdf:resource=quot;#Accommodationquot;/>
</owl:Class>
</owl:Class>
<owl:Class rdf:ID=quot;BedAndBreakfastquot;>
<owl:Class rdf:ID=quot;BedAndBreakfastquot;>
</owl:Class>
</owl:Class>
<owl:Class rdf:ID=quot;LuxuryHotelquot;>
<owl:Class rdf:ID=quot;LuxuryHotelquot;>
<rdfs:subClassOf>
<rdfs:subClassOf>
<owl:Class rdf:ID=quot;Hotelquot;/>
<owl:Class rdf:ID=quot;Hotelquot;/>
</rdfs:subClassOf>
</rdfs:subClassOf>
</owl:Class>
</owl:Class>
<owl:Class rdf:about=quot;#Hotelquot;>
</owl:Class>
</owl:Class>


Step 1b
Disjoint
Define disjoint Bed&Breakfast
Bed&Breakfast

classes Accommodation
Accommodation
Camping
Camping
Budget
Budget
Accommodation
Accommodation
Hotel
Hotel

<owl:disjointWith rdf:resource=quot;#Campingquot;/>
<owl:disjointWith rdf:resource=quot;#Campingquot;/>
<owl:disjointWith>
<owl:disjointWith>
<owl:Class rdf:about=quot;#BedAndBreakfastquot;/>
<owl:Class rdf:about=quot;#BedAndBreakfastquot;/>
</owl:disjointWith>
</owl:disjointWith>
</owl:Class>
</owl:Class>


Step 1c Activity
Activity

Sightseeing
Adventure

Define multiple
Sightseeing
Adventure

inheritance
Safari
Safari
BunjeeJumping
Museums


Step 2a Range

Accommodation
Accommodation

Define object properties hasAccommodation

relationships Domain

Destination
Destination

<owl:ObjectProperty rdf:ID=quot;hasAccommodationquot;>
<owl:ObjectProperty rdf:ID=quot;hasAccommodationquot;>
<rdfs:domain rdf:resource=quot;#Destinationquot;/>
<rdfs:domain rdf:resource=quot;#Destinationquot;/>
<rdfs:range rdf:resource=quot;#Accommodationquot;/>
<rdfs:range rdf:resource=quot;#Accommodationquot;/>


Step 2b
Define object properties characteristics
E.g: define an inverse object property

isOffered
Destination
Destination

Activity
Activity
hasActivity

<owl:ObjectProperty rdf:about=quot;#isOfferedquot;>
<owl:ObjectProperty rdf:about=quot;#isOfferedquot;>
<rdfs:range rdf:resource=quot;#Destinationquot;/>
<rdfs:range rdf:resource=quot;#Destinationquot;/>
<owl:inverseOf rdf:resource=quot;#hasActivityquot;/>
<owl:inverseOf rdf:resource=quot;#hasActivityquot;/>
<rdfs:domain rdf:resource=quot;#Activityquot;/>
<rdfs:domain rdf:resource=quot;#Activityquot;/>


int

Step 2c
hasZipCode

string
Contact
Contact
hasStreet

hasEMail string

Define datatype properties
The range specifies the
data type

<owl:DatatypeProperty rdf:ID=quot;hasEMailquot;>
<owl:DatatypeProperty rdf:ID=quot;hasEMailquot;>
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/XMLSchema#stringquot;/>
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/XMLSchema#stringquot;/>
<rdfs:domain rdf:resource=quot;#Contactquot;/>
<owl:DatatypeProperty rdf:ID=quot;hasZipCodequot;>
<owl:DatatypeProperty rdf:ID=quot;hasZipCodequot;>
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/XMLSchema#intquot;/>
<rdfs:range rdf:resource=quot;http://www.w3.org/2001/XMLSchema#intquot;/>


Step 3 OneStarRating
OneStarRating
Accommodation
Accommodation
Rating
Rating
TwoStarRating
TwoStarRating

Define individuals ThreeStarRating
ThreeStarRating

instances Family
Family
Destination
Destination

Bardonecchia
Bardonecchia
Rimini
Rimini

<AccommodationRating rdf:ID=quot;OneStarRatingquot;/>
<AccommodationRating rdf:ID=quot;ThreeStarRatingquot;/>
<AccommodationRating rdf:ID=quot;ThreeStarRatingquot;/>
<AccommodationRating rdf:ID=quot;TwoStarRatingquot;/>
<FamilyDestination rdf:ID=quot;Bardonecchiaquot;/>
<FamilyDestination rdf:ID=quot;Bardonecchiaquot;/>
<FamilyDestination rdf:ID=quot;Riminiquot;/>
<FamilyDestination rdf:ID=quot;Riminiquot;/>


Step 4
Define restrictions
To restrict the individuals that belong to a
class
Quantifier restrictions (existential, universal
quantifiers)
Cardinality restrictions
hasValue restrictions


Step 4 – example 1 Accommodation
Accommodation

hasAccommodation >= 1

FamilyDestination is a Activity
Activity

Destination
Destination
Destination with at least one hasActivity >= 2

accommodation and at least
Family
Family
2 activities Destination
Destination

Necessary and
sufficient condition

Cardinality restriction

Step 4 – example 1 FamilyDestination is a
FamilyDestination is a
Destination with at least
Destination with at least
one accommodation and
one accommodation and
at least 2 activities
at least 2 activities
<owl:Class rdf:ID=quot;FamilyDestinationquot;>
<owl:Class rdf:ID=quot;FamilyDestinationquot;>
<owl:equivalentClass>
<owl:Class>
<owl:Class>
<owl:intersectionOf rdf:parseType=quot;Collectionquot;>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty>
<owl:onProperty>
<owl:ObjectProperty rdf:ID=quot;hasAccommodationquot;/>
</owl:onProperty>
</owl:onProperty>
<owl:minCardinality rdf:datatype=quot;http://www.w3.org/2001/XMLSchema#intquot;
>1</owl:minCardinality>
</owl:Restriction>
</owl:Restriction>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty>
<owl:onProperty>
<owl:ObjectProperty rdf:ID=quot;hasActivityquot;/>
</owl:onProperty>
</owl:onProperty>
</owl:Restriction>
</owl:Restriction>
<owl:Class rdf:about=quot;#Destinationquot;/>
</owl:intersectionOf>
</owl:Class>
</owl:Class>
</owl:equivalentClass>
</owl:Class>
</owl:Class>


Step 4 – example 2
QuietDestination is a Destination Destination
Destination

that is not chosen by noisy
families Quiet
Quiet
Destination Family
Destination Family
Destination
Destination

Complement restriction


Step 4 – example 2 QuietDestination is a
QuietDestination is a
Destination that is not
Destination that is not
chosen by noisy families
chosen by noisy families
<owl:Class rdf:ID=quot;QuietDestinationquot;>
<owl:Class rdf:ID=quot;QuietDestinationquot;>
<owl:Class>
<owl:Class>
<owl:Class>
<owl:Class>
<owl:complementOf rdf:resource=quot;#FamilyDestinationquot;/>
<owl:complementOf rdf:resource=quot;#FamilyDestinationquot;/>
</owl:Class>
</owl:Class>
</owl:Class>
</owl:Class>
</owl:Class>
</owl:Class>


OneStarRating
OneStarRating

Step 4 – example 3 TwoStarRating
TwoStarRating
Accommodation
Accommodation
Rating
Rating

Bed&Breakfast
Bed&Breakfast
ThreeStarRating
ThreeStarRating

hasRating
Budget
Budget Camping
Camping
Accommodation
Accommodation

Accommodation
Accommodation

BudgetAccommodation is
an Accommodation that has Luxury Hotel
Luxury Hotel
Hotel
Hotel

either one or two star rating Sheraton
Sheraton

Existential restriction

Step 4 – example 3 BudgetAccommodation
BudgetAccommodation
is an Accommodation
is an Accommodation
that has either one or
that has either one or
two star rating
two star rating
<owl:Class>
<owl:Class>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty>
<owl:onProperty>
<owl:ObjectProperty rdf:ID=quot;hasRatingquot;/>
<owl:ObjectProperty rdf:ID=quot;hasRatingquot;/>
</owl:onProperty>
</owl:onProperty>
<owl:someValuesFrom>
<owl:Class>
<owl:Class>
</owl:oneOf>
</owl:oneOf>
</owl:Class>
</owl:Class>
</owl:someValuesFrom>
</owl:Restriction>
</owl:Restriction>
<owl:Class rdf:about=quot;#Accommodationquot;/>
<owl:Class rdf:about=quot;#Accommodationquot;/>
</owl:Class>
</owl:Class>
</owl:Class>
</owl:Class>


Bed&Breakfast
Bed&Breakfast
Hotel

Step 4 – example 4
Hotel

Camping
Camping

Accommodation
Accommodation
Budget
Budget
BackpackerDestination Accommodation
Accommodation
hasAccommodation

is a Destination that Backpacker
Backpacker
Destination
Destination
provides budget
Sports hasActivity
Sports

accommodation and Destination
Activity Destination
Relaxation Activity
Relaxation

offers sport or
Adventure
adventure activities
Adventure

Sightseeing
Sightseeing


BackpackerDestination is
BackpackerDestination is
Step 4 – example 4 a Destination that provides
a Destination that provides
budget accommodation
budget accommodation
and offers sport or
and offers sport or
<owl:Class rdf:ID=quot;BackpackerDestinationquot;>
<owl:Class rdf:ID=quot;BackpackerDestinationquot;>
<owl:Class>
<owl:Class>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty>
<owl:onProperty>
</owl:onProperty>
</owl:onProperty>
<owl:someValuesFrom rdf:resource=quot;#BudgetAccommodationquot;/>
<owl:someValuesFrom rdf:resource=quot;#BudgetAccommodationquot;/>
</owl:Restriction>
</owl:Restriction>
<owl:Restriction>
<owl:Restriction>
<owl:onProperty>
<owl:onProperty>
</owl:onProperty>
</owl:onProperty>
<owl:Class>
<owl:Class>
<owl:unionOf rdf:parseType=quot;Collectionquot;>
<owl:unionOf rdf:parseType=quot;Collectionquot;>
<owl:Class rdf:about=quot;#Sportsquot;/>
<owl:Class rdf:about=quot;#Sportsquot;/>
<owl:Class rdf:about=quot;#Adventurequot;/>
<owl:Class rdf:about=quot;#Adventurequot;/>
</owl:unionOf>
</owl:unionOf>
</owl:Class>
</owl:Class>
</owl:Restriction>
</owl:Restriction>
</owl:Class>
</owl:Class>
F. </owl:Class>
Corno, L. Farinetti- Politecnico di Torino 91
</owl:Class>

Semantic annotation
Explicit representation of a fact
A given resource...
...is related to...
...a given conceptual representation


Annotation

xxxyxyxyyx xyxyx xyxy
xyx xyxyyx yyxyyx
yxyyyx yx
xyyx xyyx yxyyyxyx
xyxyyxxy xyx xyyxyx
related
xyyx xyx yyyxyxyx
yyyxyxyyx xyyxyyx

xyxyyx yxy xyyxyx


“A given resource...”
URI
xxxyxyxyyx xyxyx xyxy
URI Content xyx xyxyyx yyxyyx
yxyyyx yx
Text xyyx xyyx yxyyyxyx
xyxyyxxy xyx xyyxyx
XML / XHTML
xyyx xyx yyyxyxyx
Multimedia yyyxyxyyx xyyxyyx

Structured documents xyxyyx yxy xyyxyx

Fragment


Resource = fragment

related
xyxyxyyx xyxyx xyxy
xyx xyxyyx yyxyyx
yxyyyx yx
related xyyx xyyx yxyyyxyx
xyxyyxxy xyx xyyxyx
related xyyx xyx yyyxyxyx
yyyxyxyyx xyyxyyx
related xyxyyx yxy xyyxyx


Resource fragmentation
Identifying fragments
Structure
XML nesting
XHTML sectioning
DIV nesting
Visual appearance
Layout reverse-engineering
Exploit common usability conventions
Discard navigation information


Pushing fragmentation to the end

Annotate each sentence, or each word
In 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 resource
Is a single concept a suitable
representation?
Weighted relationships
Conceptual spectra
Fuzzy logic
…

“…is related to…”
Annotation storage
Annotation creation
RDF (Resource
related
Description xxxx
yyxyx
Framework)


Explicit annotation
This is the DREAM of the Semantic Web
Each resource is explicitly (manually?)
annotated
by the author
by 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 project

Automatic annotation
Given a set of resources
Given an ontology
Generate 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 relevant
The documents may be in other languages
Bootstrap problem!
Need “syntactical” ties with concepts
Need “semantic” knowledge with resources


Bootstrap techniques
Provide a set of words / patterns /
sequences / rules / … for each concept
(and for each language) that “activate” the
concept
Provide a set of relevant “real” resources
classified 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 knowledge
Use user experience (Web 2.0)

License
This work is licensed under the Creative
Commons Attribution-Noncommercial-
Share Alike 3.0 Unported License.
To view a copy of this license, visit
http://creativecommons.org/licenses/by-
nc-sa/3.0/ or send a letter to Creative
Commons, 171 Second Street, Suite 300,
San Francisco, California, 94105, USA.

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