OWL 2 Web Ontology Language:

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22 Οκτ 2013 (πριν από 4 χρόνια και 22 μέρες)

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OWL 2 Web Ontology Language:
New Features and Rationale

Feroz Farazi

farazi@disi.unitn.it

Outline


Introduction


Features and rationale


Profiles


Conclusion

Introduction


OWL 2:


Extends OWL 1


Inherits OWL 1 language features


The new features of OWL 2 based on:


Real applications


User experience


Tool developer experience

Features and Rationale


Syntactic sugar


New constructs for properties


Extended datatypes


Punning


Extended annotations


Some innovations


Minor features

Features and Rationale


Syntactic sugar


Makes some patterns easier to write


Does not change


Expressiveness


Semantics


Complexity


Can help implementations


For more efficient processing


Features and Rationale


Syntactic sugar:


DisjointUnion


DisjointClasses


NegativeObjectPropertyAssertion


NegativeDataPropertyAssertion


DisjointUnion


Union of a set of classes


All the classes are pairwise disjoint

Syntactic sugar


Need for
disjointUnion

construct


A
:
CarDoor

is exclusively either


a
:
FrontDoor
,


a
:
RearDoor

or


a
:TrunkDoor



and not more than one of them


A
disjointUnion

example


<
owl:Class

rdf:about
="
CarDoor
">


<
owl:disjointUnionOf

rdf:parseType
="Collection">


<
rdf:Description

rdf:about
="
FrontDoor
"/>


<
rdf:Description

rdf:about
="
RearDoor
"/>



<
rdf:Description

rdf:about
="
TrunkDoor
"/>

</
owl:disjointUnionOf
>



</
owl:Class
>

Syntactic sugar


DisjointClasses


A set of classes


All the classes are pairwise disjoint


Need for DisjointClasses


Nothing can be both


A
LeftLung

and


A
RightLung

Syntactic sugar


NegativeObjectPropertyAssertion


Two individuals


A property does not hold between them

Example, Patient “John” does not live in “
Povo



NegativeDataPropertyAssertion


An individual


A literal


A property does not hold between them

Example, “John” is not “5” years old.

New constructs for properties


Self restriction


Qualified cardinality restriction


Object properties


Disjoint properties


Property chain


keys

Self restriction


Classes of objects that are related to
themselves by a given property


For example, the class of
processes

that
regulate themselves


It is also called
local reflexivity


An example: Auto
-
regulating processes
regulate

themselves

Qualified cardinality restrictions


Qualifies the instances to be counted


Restrain the class or data range of the
instances to be counted


For example,


Persons that have exactly three children who are
girls


Each individual has at most one SSN

Qualified cardinality restrictions


ObjectMinCardinality


ObjectMaxCardinality


ObjectExactCardinality


DataMinCardinality


DataMaxCardinality


DataExactCardinality

Object properties


ReflexiveObjectProperty


Globally reflexive


Everything is part of itself


IrreflexiveObjectProperty


Nothing can be a proper part of itself


AsymmetricObjectProperty


If x is proper part of y, then the opposite does not hold

Disjoint propertis


DisjointObjectProperties


Deals with object properties


Pairwise disjointness can be asserted


E.g., connectedTo and contiguousWith


DisjointDataProperties


Deals with data properties


Pairwise disjointness can be asserted


E.g., startTime and endTime of a surgery

Property chain inclusion


Properties can be defined as a composition of
other properties


If disease A is locatedIn body part B and B is
part of body part C then A is locatedIn C



SubObjectPropertyOf ( ObjectPropertyChain(
locatedIn partOf) locatedIn)


Keys


Individuals can be
identified uniquely


Identification can be done using


A data property


An object property or


A set of properties



HasKey
(
:
RegisteredPatient

:
hasWaitingListN

)



ClassAssertion
(
:
RegisteredPatient

:
ThisPatient

)


DataPropertyAssertion
(
:
hasWaitingListN

:
ThisPatient

"123
-
45
-
6789" )



HasKey
(
:Transplantation
:
donorId

:
recipientId

:
ofOrgan

)


Features and Rationale


Syntactic sugar


New constructs for properties


Extended datatypes


Punning


Extended annotations


Some innovations


Minor features

Extended datatypes


Extra
datatypes


For example,
owl:real

and
owl:rational


Datatype

restrictions


Range of
datatypes


For example, adult has an age >= 18


DatatypeRestriction
(
xsd:integer

minInclusive

18)


Datatype

definitions


New
datatypes


DatatypeDefinition
(
:
adultAge

DatatypeRestriction
(
xsd:integer

minInclusive

18))

Extended datatypes


Data range combinations


Intersection of


DataIntersectionOf(
xsd:nonNegativeInteger

xsd:nonPositiveInteger

)


Union of


DataUnionOf(
xsd:string

xsd:integer

)


Complement of data range


DataComplementOf(
xsd:positiveInteger

)


Punning


Punning
:
“What's
black and white and red
all
over
?”


Classes and individuals can have the same
name
thanks

to
punning


E.g., Eagle as a class and as an individual


Properties and individuals can have the same
name


E.g.,
is_located_in

as a property and as an
individual of
Deprecated_Properties

class

Punning


Classes and object properties also can have
the same name


But classes and datatype properties can not
have the same name


Also datatype properties and object
properties can not have the same name

Features and Rationale


Extended Annotations


Axioms can be annotated


For example, SubClassOf( Annotation(
rdfs:comment

"Middle lobes of
lungs are necessarily right lobes since left lungs do not have middle
lobe.")
:MiddleLobe

:RightLobe

)


Innovations


Top and Bottom properties


IRI: Internationalized Resource Identifier

Features and Rationale


Inverse object properties:


some object property can be inverse of another
property


For example, partOf and hasPart


ObjectInverseOf(
:partOf

):
this expression
represents the inverse property of
:part of


This makes writing ontologies easier by avoiding
the need to name an inverse

Outline


Introduction


Features and rationale


Profiles


Conclusion

Profiles


Profiles are sublanguages of OWL 2


Profiles considered


Useful computational properties, e.g., reasoning
complexity


Implementation possibilities, e.g., using RDBs


There are three profiles


OWL 2 EL


OWL 2 QL


OWL 2 RL


OWL 2 EL


The EL acronym reflects the profile’s basis in the
EL family of description logics


This logic is also called
small
description

logic
(DL)
EL


This logic allows
for
conjunction and
existential

restrictions


It does not allow disjunction and
universal
restrictions


It can capture the expressive power used by
many large
-
scale ontologies, e.g., SNOMED CT

OWL 2 QL


The QL acronym reflects its relation to the
standard relational Query Language


It does not allow
existential

and
universal
restrictions

to a class expression or a data range


These restrictions


enable a tight integration with RDBMSs,


reasoners

can be implemented on top of standard
relational databases


Can answer complex queries (in particular, unions
of conjunctive queries) over the instance level
(
ABox
) of the DL knowledge base

OWL 2 RL


The RL acronym reflects its relation to the Rule
Languages


OWL 2 RL is
desgined

to accommodate


OWL 2 applications that can trade the full expressivity of
the language for efficiency


RDF(S) applications that need some added expressivity
from OWL 2


Existential quantification to a class, union and disjoint
union to class expressions are not allowed


These restrictions


allow OWL 2 RL to be implemented using rule
-
based
technologies such as rule extended DBMSs

Profiles


Profile selection depends on


Expressivenss required by the application


Priority given to reasoning on classes or data


Size of the datasets


Conclusion


Most of the new features of OWL 2 in
comparing with the initial version of OWL
have been discussed


Rationale behind the inclusion of the new
features have also been discussed


Three profiles


OWL 2 EL, OWL 2 QL and OWL
2 RL, and their necessity have been presented

Thank you!

Questions?