OWL - Linked Data: A Geographic Perspective - page 178

Everything is part of itself. ObjectProperty: part_of

Characteristics: Reflexive

Note that the characteristic of reflexivity belongs to the property , not to any par-
ticular class. Alternatively, a property can be irreflexive, , meaning that no individual
can be related to itself by such a property. Previously, we used the example of a
Semidetached House as follows:

Every Semi Detached House is attached
to exactly 1 Semi Detached House.

Class: SemiDetachedHouse
SubClassof: House that
(isAttatchedTo exactly 1
SemiDetachedHouse

And we noted that this axiom allows a semidetached house to be attached to itself,
which is rather unhelpful. By making the property isAttachedTo irreflexive, then we
now ensure a semidetached house can only be attached to one other and different
semidetached house.
owl:objectHasSelf is a construct used to describe the characteristic of local
reflexivity , that is, reflexivity for individuals. It can be applied to the class of objects
(individuals) that are related to themselves via the given object property. It is useful
when reflexivity does not hold for the property globally, but for a certain number of
classes, the property will still be reflexive. For example, an autoregulating ecological
process is one that regulates itself. So, local reflexivity could be applied to the prop-
erty “regulates” if the subject is an AutoRegulatingEcologicalProcess .

Class: AutoRegulatingProcess
SubClassOf: regulates some Self

9.3.13 n egative a ssertiOns
Due to the open world nature of OWL, if we do not state a fact, it could still be true.
So if, say, we do not know whether Merea Maps is a subsidiary of the Merea Land
Management Agency, we need say nothing. However, if we definitely know that it is
not a subsidiary, and this is important for some reason, we can state this as follows:

Merea Maps is not a subsidiary of
Merea Land and Property.

Individual: MereaMaps
Facts: not isSubsidiaryOf
{MereaLandAndProperty}

OWL 2 also introduces something called a Negative Property Assertion, which
does not have a corresponding Rabbit construct:

Individual: MereaMaps
NegativeObjectPropertyAssertion: isSubsidiaryOf MereaLandAndProperty

Furthermore, OWL 2 also supports a Negative Data Property, which can be used
to model statements such as “MereaMaps does not have 100 employees.”