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If we know that Merea owns Merea Maps, then we can use the inverse property rela-
tionship between “owns” and “owned by” to infer that Merea Maps is owned by Merea.
9.3.9
s ymmetry
The relationship “next to” is
symmetric.
ObjectProperty: nextTo
Characteristics: Symmetric.
If a property such as “next to” is symmetric, then this means that if A is next to B,
then we can also infer that B is next to A.
The relationship “is larger than”
is asymmetric.
ObjectProperty: isLargerThan
Characteristics: Asymmetric.
Conversely, an asymmetric property means that if A is related to B, then B cannot
be related to A. For example, the relationship “is larger than” is asymmetric, as if
one thing is larger than another, the second thing cannot ever be larger than the first.
9.3.10
t ransitivity
The characteristic of transitivity can be seen in the following example with the prop-
erty “connected to”: If roadStretch1 is connected to roadStretch2 and roadStretch2
is connected to roadStretch3, then roadStretch1 is also connected to roadStretch3.
The relationship “connected to”
is transitive.
ObjectProperty: connectTo
Characteristics: Transitive.
As we discussed in Chapter 10, transitivity needs to be treated with care but can be
very useful.
9.3.11 f unctiOnaL , i nverse f unctiOnaL , anD K ey P rOPerties
A functional property is many to one: a property that can only have one unique
value as the object for each individual using that property. For example, “is capital
city of” can only take one value as an object, as a city can only be the capital city of
one country. “is capital city of” is also an example of an inverse functional property
(one to many), that is, one that can only have one value as the subject: Only one city
can be the capital city of a country. In Rabbit CNL and Manchester OWL Syntax,
this is stated as
The relationship “is capital city
of” can only have one object.
The relationship “is capital city
of” can only have one subject.
ObjectProperty: isCapitalCityOf
Characteristics:
InverseFunctional
ObjectProperty: hasCapitalCity
Characteristics: Functional
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