Re: Definition of Inconsistency

On Apr 3, 2013, at 8:03 AM, Magnus wrote:

> Hello,
> 
> I stumpled upon the definition of Inconsistency
> 
> "An RDF graph is inconsistent if it contains an internal contradiction. There is no possible arrangement of the world that would make the expression true."

Well, that is the glossary entry. 

> 
> Imho that makes no sense, an RDF graph can't contain an internal contradiction, since it is not possible to express negation in RDF. If I state
> 
> :Bob :sex :Male .
> :Bob :sex :Female .
> 
> it is not contradictory in RDF

True.

> , though it might be contradictory in the interpretation and understanding, someone has about the world.

Indeed, RDF has no negation, although there can be datatype clashes which produce inconsistencies. But RDF semantic extensions can encode direct contradictions in an RDF graph, and the glossary entry was intended to convey the general idea rather than be restricted to RDF.

Presumably a fuller account of the understanding that your hypothetical understander has would include something like 

:Male owl:disjointWith :Female .

which would provide the formal contradiction when added to the above (and when using OWL semantics.)

> 
> The second part does not clarify the definition, a "possible arrangement of the world" can be seen in a loose or very broad sense. Following this definition,  inconsistency lies in the eye of the beholder: an RDF graph containing 
> 
> :Buddha rdf:type :God .
> 
> would be consistent for Buddhist and for people who do not care, but inconsistent for those, believing in another god and deny the existence of any other.

True, it all depends upon what you consider to be a *possible* arrangement of the world, ie a *possible* interpretation. Formally, RDF interpretations are defined in the spec and so the scope of RDF-possible is determined there. BUt as I say, this glossary entry is intended to convey the general idea is intuitive terms. 

I am sorry if attempting to be intuitive and general-purpose has led to confusions. 

> 
> Is there any discussion about that? Can you clarify?

Does this help?

Pat

> 
> Regards
> Magnus
> 
> 
> 
> 

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Received on Wednesday, 3 April 2013 18:34:44 UTC