Re: some basic questions, thanks

>1. If A is the intersection of B and C, does it mean that A is the 
>subclass of both B and C?

Since you are referring to intersection, I presume that you are 
talking here about OWL.  In which case, yes: the intersection A is a 
subClass of both B and of C.

>Is it correct that the instances of A are also instances of B and C 
>while the common instances of B and C are also instances of A?

In OWL, yes.

>2. If  A is the union of B and C, the instances of B and C are also 
>instances of A. How does it differ from the relationship between 
>subclass and superclass where the instances of the subclass are also 
>instances of the superclass?

The union is a superclass of both the classes unioned, but there 
could be other, larger superclasses. For example, the union of the 
classes of cats and dogs is a superclass of the class of dogs, but so 
is the class of all mammals, of all animals and many other even 
larger classes; but these are all much larger than the union. (A 
union B) is the smallest superclass of both A and B.

>
>Does A have its own instances in addition to the instances of B and C?

Not 'in addition', in the sense of instances which are neither in A 
nor in B.  But if you assert that x is of type (A union B) you do not 
know whether x is in A or in B.

>
>3. If A and B are complement of each other, does it mean there 
>exists a C who is the union of A and B or the superclass of A and B?

In OWL, the union always exists, and the union of a pair of 
complementary classes is the entire universe owl:Thing.

>
>4. If a class has subclasses, does this class have instances of its 
>own in addition to the instances of its subclasses?

It may have, but this is not required.  For example, a class is a 
subClassOf itself.

I hope this helps.

Pat Hayes

>
>Thank you in advance.
>
>
>Add photos to your e-mail with 
><http://g.msn.com/8HMBEN/2746??PS=>MSN 8. Get 2 months FREE*.


-- 
---------------------------------------------------------------------
IHMC	(850)434 8903 or (650)494 3973   home
40 South Alcaniz St.	(850)202 4416   office
Pensacola			(850)202 4440   fax
FL 32501			(850)291 0667    cell
phayes@ihmc.us       http://www.ihmc.us/users/phayes