Restrictions¶
Restrictions are special type of Classes in ontology.
Restrictions on a Property¶
>>> from owlready import *
>>> onto = Ontology("http://test.org/onto.owl")
>>> class Drug(Thing):
... ontology = onto
>>> class ActivePrinciple(Thing):
... ontology = onto
>>> class has_for_active_principle(Property):
... ontology = onto
... domain = [Drug]
... range = [ActivePrinciple]
For example, a Placebo is a Drug with no Active Principle:
>>> class Placebo(Drug):
... equivalent_to = [Drug & NOT(restriction(has_for_active_principle, SOME, ActivePrinciple))]
In the example above, ‘restriction(has_for_active_principle, SOME, ActivePrinciple)’ is the Class of all objects that have at least one Active Principle. The NOT() function returns the negation of a Class. The & operator returns the intersection of two Classes.
Another example: an Association Drug is a Drug that associates two or more Active Principle:
>>> class DrugAssociation(Drug):
... equivalent_to = [Drug & restriction(has_for_active_principle, MIN, 2, ActivePrinciple)]
Owlready provides the following types of restrictions (they have the same names than in Protégé):
- some : restriction(Property Class, SOME, Range Class)
- only : restriction(Property Class, ONLY, Range Class)
- min : restriction(Property Class, MIN, cardinality, Range Class)
- max : restriction(Property Class, MAX, cardinality, Range Class)
- exactly : restriction(Property Class, EXACTLY, cardinality, Range Class)
- value : restriction(Property Class, VALUE, Range Instance)
Class operators¶
Owlready provides the following operators between Classes (normal Classes but also restrictions):
& : and operator (intersection). For example: Class1 & Class2
: or operator (union). For example: Class1 | Class2NOT() : not operator (negation). For example: NOT(Class1)
One Of restrictions¶
In ontologies, a ‘One Of’ statement is used for defining a Class by extension, i.e. by listing its Instances rather than by defining its properties.
>>> class DrugForm(Thing):
... ontology = onto
>>> tablet = DrugForm()
>>> capsule = DrugForm()
>>> injectable = DrugForm()
>>> pomade = DrugForm()
# Assert that there is only four drug forms possible
>>> DrugForm.is_a.append(one_of(tablet, capsule, injectable, pomade))