Week 3: OWL & Reasoning

RDFS Features:
- Class and property hierarchies
- Domain and range constraints

OWL Additions:
- Class restrictions (someValuesFrom, allValuesFrom)
- Cardinality constraints
- Property characteristics (transitive, symmetric)
- Class operations (union, intersection, complement)
- Equivalence and disjointness

@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix ex: <http://example.org/> .
 
# Class declarations
ex:Animal a owl:Class .
ex:Mammal a owl:Class ;
    rdfs:subClassOf ex:Animal .
ex:Bird a owl:Class ;
    rdfs:subClassOf ex:Animal .
 
# Disjoint classes
ex:Mammal owl:disjointWith ex:Bird .
 
# Equivalent classes
ex:Human owl:equivalentClass ex:Person .

# Object property (relates individuals)
ex:hasParent a owl:ObjectProperty ;
    rdfs:domain ex:Person ;
    rdfs:range ex:Person .
 
# Datatype property (relates to literals)
ex:hasAge a owl:DatatypeProperty ;
    rdfs:domain ex:Person ;
    rdfs:range xsd:integer .
 
# Inverse properties
ex:hasChild a owl:ObjectProperty ;
    owl:inverseOf ex:hasParent .

ex:isAncestorOf a owl:ObjectProperty,
                  owl:TransitiveProperty .
 
# If A isAncestorOf B and B isAncestorOf C
# Then A isAncestorOf C is inferred

ex:isSiblingOf a owl:ObjectProperty,
                 owl:SymmetricProperty .
 
# If A isSiblingOf B, then B isSiblingOf A
 
ex:isParentOf a owl:ObjectProperty,
                owl:AsymmetricProperty .

ex:hasBiologicalMother a owl:ObjectProperty,
                         owl:FunctionalProperty .
 
# Each person has exactly one biological mother
 
ex:hasSocialSecurityNumber a owl:DatatypeProperty,
                             owl:InverseFunctionalProperty .
 
# SSN uniquely identifies a person

# A Parent is someone who has at least one child
ex:Parent a owl:Class ;
    owl:equivalentClass [
        a owl:Restriction ;
        owl:onProperty ex:hasChild ;
        owl:someValuesFrom ex:Person
    ] .

# Vegetarians only eat vegetables
ex:Vegetarian a owl:Class ;
    rdfs:subClassOf [
        a owl:Restriction ;
        owl:onProperty ex:eats ;
        owl:allValuesFrom ex:Vegetable
    ] .

# A bicycle has exactly 2 wheels
ex:Bicycle a owl:Class ;
    rdfs:subClassOf [
        a owl:Restriction ;
        owl:onProperty ex:hasWheel ;
        owl:cardinality "2"^^xsd:nonNegativeInteger
    ] .
 
# A person has at least 1 parent
ex:Person rdfs:subClassOf [
    a owl:Restriction ;
    owl:onProperty ex:hasParent ;
    owl:minCardinality "1"^^xsd:nonNegativeInteger
] .

1. File > New Ontology
2. Set IRI: http://example.org/myontology
3. Classes tab > Add subclass
4. Object Properties tab > Add property
5. Reasoner > Start reasoner
6. Inferred view shows derived facts

from owlready2 import *
 
# Load ontology
onto = get_ontology("family.owl").load()
 
# Run reasoner
with onto:
    sync_reasoner()
 
# Check inferred facts
for person in onto.Person.instances():
    print(f"{person.name}: {person.is_a}")
 
# Query inferred classes
for cls in onto.classes():
    inferred_parents = cls.is_a
    print(f"{cls.name} subClassOf {inferred_parents}")

# Defined classes
ex:Person a owl:Class .
ex:hasChild a owl:ObjectProperty .
 
ex:Parent owl:equivalentClass [
    a owl:Restriction ;
    owl:onProperty ex:hasChild ;
    owl:someValuesFrom ex:Person
] .
 
# Instance data
ex:John a ex:Person ;
    ex:hasChild ex:Mary .
 
ex:Mary a ex:Person .
 
# Reasoner infers:
# ex:John a ex:Parent .

# 1. VeteranDirector: A director who has directed 3 or more movies
class VeteranDirector(Director):
    equivalent_to = [Director & directed.min(3, Movie)]
 
# 2. Blockbuster: A movie with rating >= 8.0 AND runtime >= 120 minutes
class Blockbuster(Movie):
    equivalent_to = [Movie & rating.value(lambda x: x >= 8.0)
                          & runtime.value(lambda x: x >= 120)]
 
# 3. FrequentCollaborator: An actor who has worked with the same director on 2+ movies
class FrequentCollaborator(Actor):
    # Actor who appeared in 2+ movies by the same director