1Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Knowledge and the Web

Inference on the Semantic Web

Bettina Berendt

KU Leuven, Department of Computer Science

http://people.cs.kuleuven.be/~bettina.berendt/teaching/

Last update: October 15, 2014

2Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Agenda

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

3Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Agenda

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

4Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Motivation; deductive and inductive reasoning (ex.s)

Deductive reasoning All swans are white. Tilly is a swan.

Tilly is white. Truth-preserving!

Inductive reasoning Tilly and Edda and Edwin and … are swans. Tilly and Edda and Edwin and … are white.

All swans are white. „Bringing new knowledge into the world“

5Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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(OWL slides)

http://people.cs.kuleuven.be/~bettina.berendt/teaching/2014-15-1stsemester/kaw/OWL.pdf

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Agenda

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

7Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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OWL Abstract Syntax / OWL Functional Syntax (ex. 1)

<owl:Class rdf:ID="Bus">

<rdfs:subClassOf rdf:resource="#Vehicle"/>

</owl:Class>

Class(bus partial vehicle)

XML/RDF

Functional syntax

Pro-tégé

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OWL Abstract Syntax / OWL Functional Syntax (ex. 2)

<owl:Class rdf:ID="Bus_driver">

<owl:equivalentClass>

<owl:Class>

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

<owl:Restriction>

<owl:onProperty rdf:resource="#drives"/>

<owl:someValuesFrom rdf:resource="#Bus"/>

</owl:Restriction>

<owl:Class rdf:about="#Person"/>

</owl:intersectionOf>

</owl:Class>

</owl:equivalentClass>

</owl:Class>

(in the Protégé editor:“Person and drives some Bus“ )

Class(bus_driver complete intersectionOf( person restriction(drives someValuesFrom (bus))))

9Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Agenda

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

10Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

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Examples: Class inferences (1)

Class(a:bus_driver complete intersectionOf(

a:person

restriction(a:drives someValuesFrom (a:bus))))

Class(a:driver complete intersectionOf(

a:person

restriction(a:drives someValuesFrom(a:vehicle))))

Class(a:bus partial a:vehicle)

Note: a is the namespace used throughout these examples

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Examples: Class inferences (2)

Class(a:cat_owner complete intersectionOf(

a:person

restriction(a:has_pet someValuesFrom (a:cat))))

SubPropertyOf(a:has_pet a:likes)

Class(a:cat_liker complete intersectionOf(

a:person

restriction(a:likes someValuesFrom (a:cat))))

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Examples: Class inferences (3)

Class(a:driver complete intersectionOf(

a:person

restriction(a:drives someValuesFrom(a:vehicle))))

Class(a:driver partial a:adult)

Class(a:grownup complete intersectionOf(

a:adult

a:person))

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Examples: Class inferences (4)

Class(a:sheep partial a:animal restriction(a:eats allValuesFrom (a:grass)))

Class(a:grass partial a:plant)

DisjointClasses(

unionOf(a:animal restriction(a:part_of someValuesFrom

(a:animal)))

unionOf(a:plant restriction(a:part_of someValuesFrom

(a:plant))))

Class(a:vegetarian complete intersectionOf(

a:animal

restriction(a:eats allValuesFrom

(complementOf(a:animal)))))

restriction(a:eats allValuesFrom

(complementOf(restriction(a:part_of someValuesFrom

(a:animal)))))

This was missing on your printouts

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Examples: Class inferences (5)

Class(a:giraffe partial a:animal

restriction(a:eats allValuesFrom (a:leaf)))

Class(a:leaf partial restriction(a:part_of someValuesFrom

(a:tree)))

Class(a:tree partial a:plant)

DisjointClasses(

unionOf(restriction(a:part_of someValuesFrom (a:animal))

a:animal)

unionOf(a:plant restriction(a:part_of someValuesFrom

(a:plant))))

Class(a:vegetarian complete intersectionOf(

a:animal

restriction(a:eats allValuesFrom

(complementOf(restriction(a:part_of someValuesFrom

(a:animal)))))

restriction(a:eats allValuesFrom (complementOf(a:animal)))))

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Examples: Class inferences (6)

Class(a:old_lady complete

intersectionOf(a:person a:female a:elderly))

Class(a:old_lady partial intersectionOf(

restriction(a:has_pet someValuesFrom (a:animal))

restriction(a:has_pet allValuesFrom (a:cat))))

Class(a:cat_owner complete intersectionOf(

a:person

restriction(a:has_pet someValuesFrom (a:cat))))

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Examples: Class inferences (7)Class(a:cow partial a:vegetarian)

DisjointClasses(

unionOf(a:animal restriction(a:part_of someValuesFrom (a:animal)))

unionOf(a:plant restriction(a:part_of someValuesFrom (a:plant))))

Class(a:vegetarian complete intersectionOf( a:animal

restriction(a:eats allValuesFrom

(complementOf(restriction(a:part_of someValuesFrom

(a:animal)))))

restriction(a:eats allValuesFrom (complementOf(a:animal)))))

Class(a:mad_cow complete intersectionOf(

a:cow

restriction(a:eats someValuesFrom

(intersectionOf(restriction(a:part_of someValuesFrom (a:sheep))

a:brain)))))

Class(a:sheep partial a:animal restriction(a:eats allValuesFrom (a:grass)))

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Examples: Instance inferences (1)

Individual(a:Spike type(owl:Thing)

value(a:is_pet_of a:Pete))

Individual(a:Pete

type(owl:Thing))

ObjectProperty(a:has_pet domain(a:person)

range(a:animal))

ObjectProperty(a:is_pet_of inverseOf(a:has_pet))

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Examples: Instance inferences (2)

Individual(a:Daily_Mirror type(owl:Thing))

Individual(a:Nick type(a:male)

value(a:drives a:Q123_ABC)

value(a:reads a:Daily_Mirror))

Individual(a:Q123_ABC type(a:van) type(a:white_thing))

Class(a:white_van_man complete intersectionOf(

a:man

restriction(a:drives someValuesFrom

(intersectionOf(a:van a:white_thing)))))

Class(a:white_van_man partial restriction(a:reads

allValuesFrom (a:tabloid)))

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Examples: Instance inferences (3)

Individual(a:Walt type(a:person)

value(a:has_pet a:Huey)

value(a:has_pet a:Louie)

value(a:has_pet a:Dewey))

Individual(a:Huey type(a:duck))

Individual(a:Dewey type(a:duck))

Individual(a:Louie type(a:duck))

DifferentIndividuals(a:Huey a:Dewey a:Louie)

Class(a:animal_lover complete intersectionOf(

a:person

restriction(a:has_pet minCardinality(3))))

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Examples: Instance inferences (4)

Individual(a:Minnie type(a:female) type(a:elderly)

value(a:has_pet a:Tom))

Individual(a:Tom type(owl:Thing))

ObjectProperty(a:has_pet domain(a:person)

range(a:animal))

Class(a:old_lady complete

intersectionOf(a:person a:female a:elderly))

Class(a:old_lady partial intersectionOf(

restriction(a:has_pet someValuesFrom (a:animal))

restriction(a:has_pet allValuesFrom (a:cat ))))

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Agenda

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

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Properties and existential restrictions

Yet another syntax:Read this as

intersectionOf (Pizza restriction1 restriction2)

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Primitive and defined classes

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Open world reasoning (1)

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Open world reasoning (2): Is this a Margherita Pizza?

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Open world reasoning (3): closure restrictions/axioms – what does this exclude?

27Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

27Domain and range restrictions are axioms – or: when should you not use domain/range, but restrictions instead?

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„and“ and „or“ in logics vs. in natural language, “all“ vs. “some“- what do these 2 definitions say? Is this the intention? How can it be expressed better?

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Does „only“ (allValuesFrom) imply „some“ (someValuesFrom)?

Is an EmptyPizza a VegetarianPizza?

30Berendt: Knowledge and the Web, 1st semester 2014/2015, http://www.cs.kuleuven.be/~berendt/teaching/

30„some not …“ vs. „not some …“:what does this definition say? Is this the intention? How can it be expressed better?

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Outlook

OWL: Protégé interface, XML/RDF

OWL viewed as a description logics: basics

OWL: another syntax (for the examples that follow)

OWL inference examples

Common problems in using OWL reasoning

Combining SW data: Schema/ontology matching

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Used sources

OWL specification at http://www.w3.org/TR/owl-ref/ resp.

http://www.w3.org/TR/owl2-overview/

Difference between OWL Lite, DL, and Full by Ritesh Agrawal (2007) at http://ragrawal.wordpress.com/2007/02/20/difference-between-owl-lite-dl-and-full/

OWL Abstract Syntax: A short summary here: http://www.csee.umbc.edu/courses/691s/notes/12absyntax.pdf

pp. 10ff.: Bechhofer, S. (2003). OWL Reasoning Examples. http://owl.man.ac.uk/2003/why/20031203

pp. 22ff.: Alan L. Rector, Nick Drummond, Matthew Horridge, Jeremy Rogers, Holger Knublauch, Robert Stevens, Hai Wang, Chris Wroe: OWL Pizzas: Practical Experience of Teaching OWL-DL: Common Errors & Common Patterns. EKAW 2004: 63-81.

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.107.7584

Picture credits: see PPT „comments“ field