Re: RDF Semantics for literals

On Feb 21, 2015, at 2:07 PM, Michael Brunnbauer <brunni@netestate.de> wrote:

> 
> Hello Pat,
> 
> On Sat, Feb 21, 2015 at 11:05:45AM -0600, Pat Hayes wrote:
>>> Um... what about any of those statements:
>>> 
>>> rdfs:Resource rdfs:subClassOf rdf:langString
>>> 
>>> rdfs:Resource rdfs:subClassOf xsd:string
>>> 
>>> rdfs:Resource rdfs:subClassOf xsd:int
>>> 
>>> Do they restrict the cardinality of the models?
>> 
>> Probably. These are all obviously insane, and I do not know off the top of my head what their implications would be, but they would also be insane. 
> 
> After some consideration, I'd say that at least the first two statements are
> each unsatisfiable as IR must contain all strings and all <string,language tag>
> pairs and strings and pairs are two different things. The third statement
> would then be unsatisfiable if D contains xsd:int.

Yes, I think you are right, and in fact this has consquences for a complete RDFS reasoner which I had not previously noticed (and I suspect nobody had noticed :-)

> 
> The background of my question is that it seems to me that RDF is not a formal
> system in the strict sense because the interpretation of certain literals
> is fixed.

I also think this is correct. But the 'finite-model' variant of RDF semantics described in an appendix in the RDF 1.1 semantics document would allow the universe to only contain finitely many literal values, and that situation could be finitely axiomatized (at least for the XSD literal set, in any case.) 

> I wanted to exemplify this with a counterexample to the
> Löwenheim Skolem theorem but it seems I failed :-)
> 
> I'd be interested in other reasons why those statements are insane. Identifying
> properties and classes with strings or numbers does not seem especially weird 
> to me.

But saying that *everything* is a string or a number is insane. You and I and the class of, say, salamanders are not strings or numbers. 

Pat

> 
> Regards,
> 
> Michael Brunnbauer
> 
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Received on Saturday, 21 February 2015 23:38:43 UTC