[protege-discussion] Can't classify the OWL class properly, Why?

[Timothy Redmond]

I am missing some context on this question because I am not sure what  
you know about which individuals.  But if you mean the ontology below  
then Thomas gave you exactly right answer.  It is known that the  
individual x has a pA value of y and that y happens to be in B.   If  
this was the only property value of x then we would be able to deduce  
that x is a member of C.

But the ontology below does not tell us that y is the only possible  
value.  There could be others.  These other pA values might not be in  
B.  So it does not follow that x is a member of C.  If you add the  
assertion that x has exactly one pA value as follows

Individual: x
     Types:
         A,
         pA exactly 1 owl:Thing
     Facts:
         pA  y

Then the reasoner would conclude that x is a member of C.

-Timothy


ObjectProperty: pA

Class: A

Class: B

Class: C
     EquivalentTo:
         A
         and (pA only B)

Individual: x
     Types:
         A
     Facts:
         pA  y

Individual: y
     Types:
         B


On Sep 4, 2009, at 2:26 AM, 刘康 wrote:

> I don't know how the reasoner is writed, but I think that when
> reasoner is used, the individual of class C is given, so all of the
> fillers of property pA ARE KNOWN and there is no UNMENTIONED filler of
> pA for the given individual, the reasoner can rule out the correct
> result according to the given individual and given fillers. Otherwise,
> the reasoner fails to  implement the logical of OWL and limits the
> application of OWL.
>
> 2009/9/3 Thomas Russ <tar at isi.edu>:
>>
>> On Sep 2, 2009, at 7:01 AM, 刘康 wrote:
>>
>>> if there are 3 class A, B, C is asserted, and A has the property pA.
>>> If defines the C with the assertion that C is the class A that the
>>> property pA only class B (NECESSARY & SUFFICIENT: class A, pA only  
>>> B),
>>> I find the protege can't classify the individual properly, could you
>>> tell me why?
>>
>> Open world.
>>
>> Just because all of the KNOWN fillers of the property pA happen to  
>> belong to
>> class B, it doesn't rule out the possibility that there is some  
>> UNMENTIONED
>> filler of the property pA that doesn't belong to class B.
>>
>> Open world means that classification using only, exact cardinality  
>> and
>> maximum cardinality cannot be easily made.
>>
>> There has to either be some direct assertion, or else you have to  
>> include
>> some closure information such as asserting that the individual  
>> doesn't have
>> any individual fillers except the ones that are known.  This can be  
>> done by
>> asserting that the instance belongs to the class (pA only {set of  
>> fillers of
>> pA on the individual}).
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