[Pellet-users] Check for no subclass

[Alexander Musidlowski]

Hi,

thx for your explanation and yes, i was confused therefore i wrote to
this list :D
Maybe a little summary of my understanding. If A subclass of B and B
subclass of A then A equivalent to B. That´s just logic. If there is
no subclass then i get owl:nothing because owl:nothing is subclass of
every class by definition.
If a class is equivalent to owl:nothing this would mean this class is
an empty set (in logical sense). This class doesn´t have any
instances. So if there is a class with some instances it can´t be
equivalent to owl:nothing but it can be that there is no equivalent
class, so it returns an empty set which does not mean that is
equivalent to an empty set.
I think that´s to point, there are two different meanings which
you should know. One is the "empty" Class and the other means just
there is no class.

Thx! 

--
Bye
Alex

on Sunday, February 24, 2008 at 18:39 Pellet-users Pellet-users wrote:

> On Feb 24, 2008, at 2:58 PM, Bijan Parsia wrote:

>> On Feb 24, 2008, at 1:55 PM, Alexander Musidlowski wrote:
>>
>>> Hi,
>>>
>>> i think you refer to the sentence "and owl:Nothing is a subclass of
>>> every class". As EquivalentClass is a SubProperty of Subclass
>>
>> I don't know where you got that idea, but it's not true. Neither is
>> subclass a subproperty of equivalentclass.

> What a brain fart. I get confused by the "property" talk with regard  
> to connectives.

> "subproperty" just means "only  if"; equivalent means "iff". If A is  
> equivClass to B, then A is a subclass of B (and B is a subclass of A).
> [snip pretty much ok reasoning but still might be confusing]

>>> shouldn´t it also return owl:nothing?
>>
>> As you can see above, no.
> [snip]

> If equivalentClass(A,B) then subclass(A,C), NOT if subclass(A,B) then
> equivalentClass(A,B).

> So, owl:Nothing being a subclass of a class tells us nothing about  
> what its equivalent to. Or, equivalently., what is a subclass of  
> owl:Nothing.

> So, still no :) I hope this is clearer.

> Cheers,
> Bijan.
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