Knowledge Representation Part VII Protégé / RDFS / OWL / ++ Much of the content of this presentation has been copied from: A Practical Guide To Building OWL Ontologies Using Protégé 4 and CO-ODE Tools Edition 1.3, Matthew Horridge Jan Pettersen Nytun, UiA

Outline Property Characteristics OWL Restrictions

Knowledge Representation Part II, JPN, UiA OWL Property types There are two main types of properties: Object properties. Datatype properties. Additionally: Annotation properties can be used to add metadata (data about data). Knowledge Representation Part II, JPN, UiA

Property Characteristics OWL allows the meaning of properties to be enriched through the use of property characteristics. Knowledge Representation Part III, JPN, UiA

Knowledge Representation Part III, JPN, UiA Inverse Property If some property links individual A to individual B then its inverse property will link individual B to individual A. If Matthew hasParent Jean, then because of the inverse property we can infer that Jean hasChild Matthew. Knowledge Representation Part III, JPN, UiA

Functional Properties A functional property connects only one object or literal to a subject. birth mother: One's biological mother E.g., it is only possible to have one birth mother Knowledge Representation Part III, JPN, UiA

Functional Properties Continues … Mapping functional property to UML: It is possible to define an association as functional by specifying the upper multiplicity of the navigable end as being 0..1 Person isBirthMotherTo * birth mother: One's biological mother 0..1 Female hasBirthMother Knowledge Representation Part III, JPN, UiA

Inverse Functional Properties If a property is inverse functional then it means that the inverse property is functional. birth mother: One's biological mother Knowledge Representation Part III, JPN, UiA

Functional / Inverse Functional Properties Inverse functional properties are similar, but in the reverse direction. Person isBirthMotherTo Inverse Functional Property * birth mother: One's biological mother Functional Property 0..1 Female hasBirthMother JPN, UiA

Functional / Inverse Functional Properties continues … Both object properties and datatype properties can be declared as "functional“ but only object properties can be decleared to be “functional inverse”. RDF does not allow literal values as the subjects of triples. I seems this is why we need both???

More Property Characteristics If a property is transitive, and the property relates individual a to individual b, and also individual b to individual c, then we can infer that individual a is related to individual c via property P. E.g., subRegionOf JPN, UiA

More Property Characteristics If a property P is symmetric, and the property relates individual a to individual b then individual b is also related to individual a via property P. E.g., hasSibling JPN, UiA

More Property Characteristics If a property P is asymmetric, and the property relates individual a to individual b then individual b cannot be related to individual a via property P. E.g., isMotherTo JPN, UiA

More Property Characteristics A property P is said to be reflexive when the property must relate individual to itself. E.g., hasRelative (everybody has himself as a relative). This does not necessarily mean that every two individuals which are related by a reflexive property are identical. birth mother: One's biological mother JPN, UiA

More Property Characteristics parentOf More Property Characteristics Irreflexive, meaning that no individual can be related to itself by such a role. E.g., hasParent birth mother: One's biological mother Knowledge Representation Part III, JPN, UiA

Outline Property Characteristics OWL Restrictions

[4]: In OWL classes are built up of descriptions that specify the conditions that must be satisfied by an individual for it to be a member of the class.

OWL Restrictions Three main categories: Quantifier Restrictions existential restrictions universal restrictions Cardinality Restrictions hasValue Restrictions

A restriction describes a class of individuals based on the relationships that members of the class participate in. A restriction describes an anonymous class.

Quantifier Restrictions Existential restrictions – some Describe classes of individuals that participate in at least one relationship along a specified property to individuals that are members of a specified class. Universal restrictions – only Describe classes of individuals that for a given property only have relationships along this property to individuals that are members of a specified class.

New version of Protégé calls it “Subclass of”

Existential Restrictions A restriction containing an owl:someValuesFrom constraint describes a class of all individuals for which at least one value of the property concerned is an instance of the class description or a data value in the data range.

Cardinality in dialog window should be ignored (it is 1..*)

In Turtle Representation pizza:Pizza rdf:type owl:Class ; rdfs:label "Pizza"@en ; rdfs:subClassOf [ rdf:type owl:Restriction ; owl:onProperty pizza:hasBase ; owl:someValuesFrom pizza:PizzaBase ] ; … At least one pizza base!

pizza:Margherita rdf:type owl:Class ; rdfs:label "Margherita"@pt ; rdfs:subClassOf pizza:NamedPizza , [ rdf:type owl:Restriction ; owl:onProperty pizza:hasTopping ; owl:allValuesFrom [ rdf:type owl:Class ; owl:unionOf ( pizza:MozzarellaTopping pizza:TomatoTopping ) ] ] , … Only = owl:allValuesFrom

There is no “+” for adding; conditions comes from superclass!

Multiple Inheritance from Anonymous Classes :Pizza rdf:type owl:Class ; rdfs:subClassOf [ rdf:type owl:Restriction ; owl:onProperty :hasTopping ; owl:someValuesFrom :PizzaTopping ] , [ rdf:type owl:Restriction ; owl:onProperty :hasBase ; owl:someValuesFrom :PizzaBase ] .

References [1] Book: David Poole and Alan Mackworth, Artificial Intelligence: Foundations of Computational Agents, Cambridge University Press, 2010, http://artint.info/ [2] http://www.w3.org/TR/swbp-n-aryRelations/ [3] RDF 1.1 Primer, W3C Working Group Note, 24 June 2014 [4] A Practical Guide To Building OWL Ontologies Using Protégé 4 and CO-ODE Tools Edition 1.3, Matthew Horridge [5] http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/