Re: Comments on last-call SPARQL draft 20050721, section 2

Bijan Parsia wrote:
>>> Section 2.3
>>> Concerning the reference to literals-as-subjects.  Is this still an  
>>> option for the Semantic Web family?  I understand that OWL (or  
>>> OWL-DL) requires that subjects be URIs.  Maybe not a problem, but I  
>>> thought I'd mention it.
>>
>>
>> Not editorial.
>> Comments?
> 
> 
> RDF through OWL syntactically forbids literals-as-subjects. However,  
> OWL Full allows for equality relations between data values and abstract  
> individuals. So, semantically, there is already a sense in which the  
> OWL Family allows for literal subjects.
> 
> Furthermore, there a smooth path to OWL-DL with subjects as  
> literals...first order logic certainly allows for the first place of  
> two place predicates to have data values (when it admits such values at  
> all) and OWL-DL is a proper subset of FOL. It could be that certain  
> extensions to literal subjects would be undecidable, but so's SWRL for  
> example. I would expect that a forml of AL-Log would allow for literal  
> subjects and robust decidability.
> 
> In fact, if you were careful about equalities and class membership, it  
> might be a reasonable addition to regular OWL-DL.
> 
> Hope this helps.

Yes, thanks for clarifying.  I thought it might come out as something 
like this, but it's good to have an OWL expert confirm this.

#g

-- 
Graham Klyne
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