Re: typo in OWL 2 structural specification, not semantics.

On Nov 7, 2008, at 1:15 PM, Boris Motik wrote:

> Yes, you're right. I'm sorry - I got confused.

Yes, I agree, Bijan is right, contrary to my original note.

Still, this is VERY confusing. I would suggest that the use of  
"positive zero" and the notation "+0", while I am sure well-meant, is  
responsible for much of the difficulty. The whole idea of a "positive  
zero" is incoherent in any case, and the positive/negative contrast  
and the symmetry of the notation both strongly suggest a symmetry in  
the underlying structure, which in fact is quite asymmetric.

If this convention is already in widespread use, I guess y'all have to  
go with it;  but if not, I'd strongly suggest getting rid of 'positive  
zero' and '+0', and just calling it 'zero' and writing '0'. You know,  
like people have for about a millennium now.

Another thing that is highly confusing in the text is the use of  
'equal' having a distinct meaning from 'identical'. If these are not  
synonyms, then 'equal' does not mean =. Boris, I think your first  
response was confused on exactly this issue.

I think what y'all mean by

  "+0 is equal to -0 but not identical to it"

is in fact

"+0 isn't equal to -0 but they are equivalent as far as arithmetic is  
concerned"

Pat

PS. I presume the ordering intended is

-INF < any negative real < either zero < any positive real < +INF

but without any order assigned to {zero, -zero}.  Is this right?

> I've now reverted the spec into the original condition. While doing  
> this, I've just
> noticed that we haven't defined the relationship between -0 and +INF  
> and -INF. Therefore, I've added the following condition:
>
> * -INF < -0 < +INF
>
> Again, sorry for the confusion.
>
> Regards,
>
> 	Boris
>
>> -----Original Message-----
>> From: Bijan Parsia [mailto:bparsia@cs.man.ac.uk]
>> Sent: 07 November 2008 19:06
>> To: Boris Motik
>> Cc: 'Pat Hayes'; public-owl-wg@w3.org
>> Subject: Re: typo in OWL 2 structural specification, not semantics.
>>
>> On 7 Nov 2008, at 18:55, Boris Motik wrote:
>>
>>> Hello,
>>>
>>> Strictly speaking, this wasn't a typo because -0 is equal +0. I can
>>> see, however, that this can confuse people, so I've therefore
>>> changed the document as you've suggested.
>>>
>>> Thanks for this comment!
>>
>> Actually, I think this is a bit misleading and may even change the
>> meaning.
>>
>> +0 is a real, thus covered by the first clause (we should switch
>> these to an ordered list).
>>
>> -0 is *not* a real (though it is equal to a real), so, just like -INF
>> and +INF needs an additional clause.
>>
>> (At the moment, I don't see a hook up between = and <. As far as I
>> can tell, it's possible for -0 = +0 *and* -0 < +0. Indeed, if you
>> change the definition to +0, then I would say that -0 is not < than
>> any other element in realPlus and vice versa.)
>>
>> For example, with this change, I believe your example no longer
>> holds. I.e., from that definition -1 and 1 only have +0 between them.
>>
>> Cheers,
>> Bijan.
>
>
>
>

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Received on Friday, 7 November 2008 22:04:34 UTC