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Re: Why do you want to do that?

From: Richard H. McCullough <rhm@PioneerCA.com>
Date: Sat, 9 Aug 2008 00:01:34 -0700
Message-ID: <D254C514489444C1A9F7056A7D7FEB78@rhmlaptop>
To: "Frank Manola" <fmanola@acm.org>
Cc: "SWIG" <semantic-web@w3.org>

"in the wild"?
Excellent question.
No, I'm not seeing a lot.
As best I recall, it appeared in an introductory paper on RDF,
and was presented as if it was a neat feature of RDF.
I think the actual statement might have been
    Class  subClassOf  Class;
That led me to think it might be used a lot -- as part
of an inference.

This is what REALLY bothers me.
    X  subClassOf  Y;
leaves unresolved whether
    X  sameAs  Y;
or 
    X  properSubClassOf  Y;  
To me, that is an "annoying" question that is relevant
in inferences -- a question that you don't want to "pop up"
every time you declare a subClass.
I would guess that 99.44% of subClassOf declarations
are intended to be properSubClassOf declarations --
but  properSubClassOf is not part of the RDF vocabulary.

Dick

----- Original Message ----- 
From: "Frank Manola" <fmanola@acm.org>
To: "Richard H. McCullough" <rhm@pioneerca.com>
Cc: "SWIG" <semantic-web@w3.org>
Sent: Friday, August 08, 2008 3:14 PM
Subject: Re: Why do you want to do that?


> Dick--
> 
> 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.
> 
> --Frank
> 
> 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
>>>
>>
>>
> 
>
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/
Received on Saturday, 9 August 2008 07:07:19 GMT

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