BBY 464 Semantic Information Management
(Spring 2016)
Ontologies and
OWL: Web Ontology Language
Yaşar Tonta & Orçun Madran
[yasartonta, orcunmadran]@gmail.com
Hacettepe University
Department of Information Management
Semantic Web
From Syntactic to Semantic
Interoperability
Ontologies
Ontologies (cont’d)
• Definition and classification of concepts and
entities, and the relationships between them
• Based on basic elements of RDF
• Adds more vocabulary for describing
properties and classes
Classes
•
•
•
•
•
•
Person
Country
Animal
Book
Author
...
Instances
Properties
• Person has first name, middle initial, last
name, birthdate, age. . . as properties
• Book has author, title, place of publication . . .
as properties
• ...
Relations
More vocabulary?
• Relationship between classes (eg,
disjointWith)
• Equality (eg, sameAs)
• Richer properties (eg, symmetrical)
• Class property restrictions (eg, allValuesFrom)
Relationship between classes
• disjointWith – resources belonging to one class
cannot belong to the other
<Person> <disjointWith> <Country>
• complementOf – members of one class are all
the resources that do not belong to the other
<InanimateThings> <complementOf>
<LivingThings>
Equality
• sameAs – indicates that two resources
actually refer to the same real-world thing or
concept
<tonta> <sameAs> <yasartonta>
• Equivalent class – indicates that two classes
have the same set of members
<CoopBoardMembers>
<equivalentClass>
<CoopResidents>
Richer properties
• Symmetric – a relationship between A and B is
also true between B and A
<DavidBeckham> <marriedTo>
<VictoriaBeckham> implies
<VictoriaBeckham> <marriedTo>
<DavidBeckham>
• Transitive – a relationship between A and B and
between B and C is also true between A and C
<piston> <isPartOf> <engine>
<engine> <isPartOf> <automobile> implies
<piston> <isPartOf> <automobile>
Class property restrictions
• Define the members of a class based on their
properties
• allValuesFrom – resources with properties
that only have values that meet this criteria
– Example: Property: hasParents, allValuesFrom:
Human
– Resources that meet this criteria can be defined as
also being members of the Human class
Class property restrictions (cont’d)
• someValuesFrom – resources with properties
that have at least one value that meets criteria
– Example: Property: hasGraduated,
someValuesFrom: College
– Resources that meet this criteria can be defined as
being members of the CollegeGraduates class
Seems complicated? Why do it?
• These capabilities allows systems to express
and make sense of first-order logic
– All humans are mortal
– Socrates is a human
– Therefore, Socrates is mortal
First-order logic?
• But, first, let’s describe propositional logic
• “Yaşar is professor”. This is a proposition in classical
logic and it is either true or false.
• So is “Orçun is professor”
• These two propositions can only be combined with
defined operators
• Let’s call these two propositions p and q, respectively
• p=>q (if Yaşar is professor, then Orçun is professor, too)
• p∧q; p∨q; ≠p
• Above propositions will produce either true or false.
First-order logic? (cont’d)
• First-order logic uses quantifiers (or variables) to
model.
• Take “Yaşar is professor”, for example.
• Yaşar (a) =>Professor (a)
• Interpretation: There exists an a whose name is
Yaşar and who is professor.
• What kind of “a” is this? Is it applicable to all
“a”s? Is it true for every case?
• No. (Otherwise, all persons with the name Yaşar
should be professor!)
First-order logic? (cont’d)
• There are two symbols in first-order logic:
•
(every, all) and (there exists such that)
•
a(Yaşar (a) ∧ Professor(a) -> There exists
such a’s whose name is Yaşar and who is
Professor
• a a (Children’s librarian (a) => Librarian (a) ->
For all a’s, if a is Children’s librarian, then a is
at the same time is Librarian
Inferences
• Create new triples based on existing ones
• Deduce new facts based on stated facts
<piston> <isPartOf> <engine>
<engine> <isPartOf> <automobile> implies <piston>
<isPartOf> <automobile>
Vocabularies
Data
OWL: Web Ontology Language
• Three flavors of OWL
• OWL Lite: uses a subset of the capabilities
• OWL DL: uses all capabilities, but some are
used in restricted ways
• OWL Full: unrestricted use of capabilities; no
guarantee that all resulting statements are
valid.
OWL
Web Protege
Beer Ontology
BibFrame
DCterms
CIDOC CRM
Exercise
• Pls visit webprotege.stanford.edu and register
(free).
• Make yourselves familiar with various types of
ontologies created using OWL and explore the
classes, properties and relationships defined.
• The next step would be to create your own
ontology using OWL and upload it to
webprotege web site (details coming).
Sources used
• R. Lovinger, RDF & OWL,
http://www.slideshare.net/rlovinger/rdf-andowl?qid=c254fb47-da1e-4335-99a9199b2b65ecba&v=&b=&from_search=1
• D. Willems, What is an ontology?
http://www.slideshare.net/don_willems/what-areontologies/2COMMIT_EFOODLABIn_computer_science_and
• Ş.E. Şeker, Birinci derece mantık (First order logic),
http://bilgisayarkavramlari.sadievrenseker.com/2010/03/24
/birinci-derece-mantik-first-order-logic/