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Re: Why do you want to do that?

From: Frank Manola <fmanola@acm.org>
Date: Fri, 8 Aug 2008 18:14:10 -0400
To: "Richard H. McCullough" <rhm@pioneerca.com>
Message-Id: <20D2AA81-130C-4F48-81BA-45A2488D0D4D@acm.org>
Cc: SWIG <semantic-web@w3.org>


I'm still not entirely sure I understood what's going on.  If a lot of  
people are writing triples like

ex:Foo rdfs:subClassOf ex:Foo

(do you have any examples of this "in the wild"?  you said in your  
original message that this was a feature that "seemed to be popular",  
so I was assuming you were seeing triples like this a lot) it's not  
clear to me that changing the meaning of rdfs:subClassOf has a helpful  
effect:  with the current meaning, it's always true, with your changed  
meaning, it's always false.

As a general matter, though, I think the reason for having  
rdfs:subClassOf "be improper" is that it's a weaker semantic condition  
that having it mean proper inclusion, and RDF (and, to an extent,  
RDFS) was intended to have rather minimal semantics.  Imposing  
stronger semantic conditions was felt to be the job of "higher  
level" (if you will) languages (like OWL).  Note that RDFS also  
doesn't include anything like sameAs either.


On Aug 8, 2008, at 12:32 PM, Richard H. McCullough wrote:

> Hi Frank
> Thanks for your response.
> 2. I'll look at that.
> 1. I'm asking why would people want to write X  subClassOf  X;
> I had proposed that properSubClassOf be used instead of subClassOf.
> The former is not a very appealing name.  If, instead, we change the  
> meaning
> of subClassOf to exclude the sameAs possibility, and keep the name  
> subClassOf,
>   X  subClassOf  X;
> is false.
> Dick McCullough
> Ayn Rand do speak od mKR done;
> mKE do enhance od Real Intelligence done;
> knowledge := man do identify od existent done;
> knowledge haspart proposition list;
> http://mKRmKE.org/
> ----- Original Message ----- From: "Frank Manola" <fmanola@acm.org>
> To: "Richard H. McCullough" <rhm@pioneerca.com>
> Sent: Friday, August 08, 2008 9:01 AM
> Subject: Re: Why do you want to do that?
>> On Aug 8, 2008, at 11:21 AM, Richard H. McCullough wrote:
>>> Over the last six years, I have suggested a number of
>>> "improvements" to the RDF language.  Not one of
>>> my suggestions was adopted.  Apparently,
>>> RDF is fine just the way is, thank you!
>> Yep.  That doesn't imply opposition to improvements though;  some   
>> people think the way to provide the "improvements" they want is to   
>> define languages "on top of" RDF (like the OWL dialects) rather  
>> than  making those changes directly in RDF.  That way, your  
>> "improvement"  and my improvement can possibly co-exist more  
>> nicely :-)
>>> I would now like to turn the tables, and ask
>>> why do you want to do that?
>>> I'll start with two features of RDF which seem to be popular.
>>> 1. X  subClassOf  X;
>>> A neat mathematical property, right?
>>> But if you do the inferences, what it means is
>>>  X  sameAs  X;
>>> We already knew that.
>>> Why do you want to do that?
>> I need some help with this question.  Do you think being able to  
>> say X subClassOf Y is OK?  If so, are you asking why RDFS (not RDF,  
>> BTW) doesn't explicitly forbid the special case of X subClassOf X?   
>> Why do  you want to do that (i.e., test for this special case all  
>> the time)?   Or are you asking why people *write* X subClassOf X?
>>> 2. X  type  Y;  X  subClassOf  Z;
>>> Another neat property: X is an individual and a class.
>>> Now I can ... What?  I don't know.
>>> Why do you want to do that?
>> How about the example in Section 3.1.3 of the OWL Guide?
>> --Frank
Received on Friday, 8 August 2008 22:14:52 UTC

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