OWL reasoners use open world reasoning. So the reasoner invents
an anonymous individual of type 'Water' and adds a 'livesIn' edge
from 'Goldfish' to satisfy the constraint that Fish is a subclassOf
livesIn some Water. The idea here is that we all know Fish live in
some Water, but we may not always know which body of water it is.
Hope this helps.
On Oct 18, 2009, at 8:04 AM, Mark A. Hatcher wrote: (02)
> Dear all,
> I have struggled for too long by myself to try and understand the
> following. If anyone can help, it would be much appreciated.
> I create a class in OWL and then define a subclass restriction on this
> class. I then create an instance of the class with no restriction. I
> do not understand why the reasoner does not complain that an
> instance of
> the class exists without this restriction.
> Maybe this is easier to understand with a specific example:
> Two classes: Water and Fish.
> Restriction: Fish subclassOf livesIn some Water
> Two instances: Goldfish type Fish, River some Water.
> I do not understand the following:
> Goldfish is a member of Fish.
> Fish implies (livesIn some Water)
> I have /*not */implemented the restriction but the reasoner does not
> complain. Goldfish is a member of the class and therefore the
> restriction is implied. The reasoner does not seem to see things
> this way.
> Any help would be appreciated.
> Thanks in advance,
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