1. ece 720 intelligent web: ontology and beyond
lecture 8: owl – language I

2. OWL XML/RDF syntax: header
<rdf:RDF
xmlns:owl ="
xmlns:rdf ="
xmlns:rdfs="
xmlns:xsd ="
an OWL ontology may start with a collection of assertions for housekeeping purposes using owl:Ontology element
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3. owl:Ontology <owl:Ontology rdf:about="">
<rdfs:comment>An example OWL ontology </rdfs:comment>
<owl:priorVersion
rdf:resource="
<owl:imports
rdf:resource="
<rdfs:label>University Ontology</rdfs:label>
</owl:Ontology> …
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4. owl:Ontology
owl:imports
means an ontology O1 imports another ontology O2, and then the entire set of declarations in O2 is appended to O1
importing ontology O2 will also import all of the ontologies that O2 imports
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5. classes classes are defined using owl:Class
owl:Class is a subclass of rdfs:Class
<owl:Class rdf:about="#associateProfessor”/>
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6. classes (2) disjointness of classes is defined using owl:disjointWith
<owl:Class rdf:about="#associateProfessor">
<owl:disjointWith rdf:resource="#professor"/>
<owl:disjointWith rdf:resource="#assistantProfessor"/>
</owl:Class>
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7. classes (3) owl:equivalentClass defines equivalence of classes
<owl:Class rdf:ID="faculty">
<owl:equivalentClass rdf:resource="#academicStaffMember"/>
</owl:Class>
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8. classes (4)
owl:Thing
is the most general class, which contains everything
owl:Nothing
is the empty class
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9. properties in OWL there are two kinds of properties
object properties, which relate objects to other objects
for example, is-TaughtBy, supervises
data type properties, which relate objects to datatype values
for example, phone, title, age
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10. datatype properties
OWL makes use of XML Schema data types, using the layered architecture of the Semantic Web
<owl:DatatypeProperty rdf:ID="age">
<rdfs:range rdf:resource= "
#nonNegativeInteger"/>
</owl:DatatypeProperty>
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11. object properties user-defined data types
<owl:ObjectProperty rdf:ID="isTaughtBy">
<owl:domain rdf:resource="#course"/>
<owl:range rdf:resource="#academicStaffMember"/>
<rdfs:subPropertyOf rdf:resource="#involves"/>
</owl:ObjectProperty>
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12. property restrictions introduction – anonymous superclass
in OWL we can declare that the class C satisfies certain conditions
all instances of C satisfy the conditions
this is equivalent to saying that C is subclass of a class C', where C' collects all objects that satisfy the conditions
C' can remain anonymous
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13. property restrictions introduction – anonymous superclass
a (restriction) class is achieved through an owl:Restriction element
this element contains an owl:onProperty element and one or more restriction declarations
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14. property restrictions introduction – anonymous superclass
1 <owl:Class rdf:about=C> …
3 <rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource=P/>
6 … declaration of restriction R …
</owl:Restriction>
8 </rdfs:subClassOf> …
10 </owl:Class> in Set Theory
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15. property restrictions introduction – anonymous superclass
lines 4 to 7 define the (unnamed) class fo all things that satisfy R
line 3 indicates that C is a sublass of such a (unnamed class)
the pattern in lines 3 to 8 may be repeated to define multiple restrictions for the same class
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16. property restrictions (2)
three types of restrictions:
quantified restrictions
value restrictions (filler information)
cardinality restrictions
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17. property restrictions (3)
quantified restrictions
owl:allValuesFrom specifies universal quantification (C P.D)
owl:someValuesFrom specifies existential quantification (C P.D)
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18. property restrictions (4)
value restrictions
owl:hasValue specifies a specific value
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19. property restrictions (5)
cardinality restrictions
owl:cardinality specifies the exact number of occurences of P each instance of C must have
owl:maxCardinality (owl:minCardinality)specifies the max (min) number of occurences of P each instance of C must have
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20. owl:someValuesFrom <owl:Class rdf:about="#academicStaffMember">
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource="#teaches"/>
<owl:someValuesFrom rdf:resource="#undergraduateCourse"/>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
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21. owl:allValuesFrom <owl:Class rdf:about="#firstYearCourse">
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource="#isTaughtBy"/>
<owl:allValuesFrom rdf:resource=”#professor"/>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
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22. owl:hasValue <owl:Class rdf:about="#mathCourse">
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource="#isTaughtBy"/>
<owl:hasValue rdf:resource="#949352"/>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
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23. cardinality restrictions
<owl:Class rdf:about="#course">
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource="#isTaughtBy"/>
<owl:Cardinality rdf:datatype="&xsd;nonNegativeInteger"> 1
</owl:Cardinality>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
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24. properties of object properties
owl:TransitiveProperty
for example, “has better grade than”, “is ancestor of”
R is transitive iff,
for any x, y and z, if R(x,y) and R(y,z) then R(x,z)
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25. properties of object properties (2)
owl:SymmetricProperty
for example, “has same grade as”, “is sibling of”
R is symmetric iff,
for any x, y, R(x,y) iff R(y,x)
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26. properties of object properties (3)
owl:FunctionalProperty defines a property that has at most one value for each object
for example, “age”, “height”, “directSupervisor”
R is functional iff,
for any x, y and z, if R(x,y) and R(x,z) then y=z
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27. properties of object properties (4)
owl:InverseFunctionalProperty defines a property for which two different objects cannot have the same value
R is inverse functional iff,
for any x, y and z, if R(y,x) and R(z,x) then y=z
(only for OWL Full)
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28. properties of object properties (5)
owl:InverseOf
S is the inverse of R iff,
for any x, y, R(x,y) iff S(y,x)
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29. properties of object properties – example
<owl:ObjectProperty rdf:ID=”isTaughtBy">
<rdf:type rdf:resource="&owl;FunctionalProperty"/>
<owl:domain rdf:resource="#course"/>
<owl:range rdf:resource="#academicStaffMember"/>
</owl:ObjectProperty>
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30. properties of object properties – example
<owl:ObjectProperty rdf:ID="hasSameGradeAs">
<rdf:type rdf:resource="&owl;TransitiveProperty"/>
<rdf:type rdf:resource="&owl;SymmetricProperty"/>
<rdfs:domain rdf:resource="#student"/>
<rdfs:range rdf:resource="#student"/>
</owl:ObjectProperty>
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31. properties of object properties – example
<owl:ObjectProperty rdf:ID="teaches">
<rdfs:range rdf:resource="#course"/>
<rdfs:domain rdf:resource="#academicStaffMember"/>
<owl:inverseOf rdf:resource="#isTaughtBy"/>
</owl:ObjectProperty>
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32. properties of object properties – example
owl:equivalentProperty
<owl:ObjectProperty rdf:ID="lecturesIn">
<owl:equivalentProperty rdf:resource="#teaches"/>
</owl:ObjectProperty>
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