BBY 464 Semantic Information Management (Spring 2016) Ontologies and OWL: Web Ontology Language Yaşar Tonta & Orçun Madran [yasartonta, 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 complementOf – members of one class are all the resources that do not belong to the other

Equality sameAs – indicates that two resources actually refer to the same real-world thing or concept Equivalent class – indicates that two classes have the same set of members

Richer properties Symmetric – a relationship between A and B is also true between B and A implies Transitive – a relationship between A and B and between B and C is also true between A and C implies

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 implies

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, owl?qid=c254fb47-da1e a9- 199b2b65ecba&v=&b=&from_search=1 owl?qid=c254fb47-da1e a9- 199b2b65ecba&v=&b=&from_search=1 D. Willems, What is an ontology? ontologies/2- COMMIT_EFOODLABIn_computer_science_and ontologies/2- COMMIT_EFOODLABIn_computer_science_and Ş.E. Şeker, Birinci derece mantık (First order logic), /birinci-derece-mantik-first-order-logic/ /birinci-derece-mantik-first-order-logic/