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Re: RDF Extensibility

From: Jakub Kotowski <jakubkotowski@gmx.net>
Date: Fri, 09 Jul 2010 11:42:37 +0200
Message-ID: <4C36EF0D.20607@gmx.net>
To: Henry Story <henry.story@gmail.com>
CC: Bernhard Schandl <bernhard.schandl@univie.ac.at>, Reto Bachmann-Gmuer <reto.bachmann@trialox.org>, Pat Hayes <phayes@ihmc.us>, Linked Data community <public-lod@w3.org>, Semantic Web <semantic-web@w3.org>
Henry Story schrieb:
> On 9 Jul 2010, at 09:29, Bernhard Schandl wrote:
> 
>> Hi,
>>
>>> I agree with Pat in that case, that it would just be easier not to put restrictions
>>> in the abstract rdf syntax at all, instead of complicating things all over the place.
>>> There are pragmatic reasons why sentences such as 
>>>
>>> <http://bblfish.net/#hjs> "name" "Henry" .
>>>
>>> are not going to be successful, the main one being that it is impossible to 
>>> adjudicate what the relation "name" refers to is about.
>> In that respect, "name" is not different than any URI one has never seen before. What about adding
>>
>> "name" rdfs:subPropertyOf foaf:name .
>>
>> to this example?
> 
> That would be an interesting theory one could have.
> 
> But what if someone else, whom you never met, had decided
> that
> 
> "name" rdfs:subPropertyOf nuclear:NuclearAtomMustExplode .
> 
> and he published information with that meaning.
> 
<snip>
> Or put it differently, if you come across a triple with a pure string
> literal relation, how would you know what relation the literal
> was referring to? Where is the ontology to be found?
> 
<snip>
>    those types of issue seem to me to indicate that it is not practical to
> have pure string literals in predicate position. The only solution will be to
> assign some name space to them, such as 
> 
>   <http://bblfish.net/#hjs> "name"^^<http://xmlns.com/foaf/0.1/> "Henry" .
> 
> And as soon as a name space is assigned we can get going again.

This looks more like a typed literal, not a namespace.

Otherwise, if literals somehow really had a namespace then you could use
the idea of ontology hijacking [1] to decide which RDF graphs are
authoritative and which not.

The problem is that literals don't have a namespace and they are not
some meaningless local part of a URI, literals are resources the same
way URIs are. So it seems triples like:

"name" rdfs:subPropertyOf nuclear:NuclearAtomMustExplode .

would always be not authoritative (literals have no namespace therefore
there is no source that speaks authoritatively about them). In this
sense, inferences that use such triples would not be authoritative but
they could well make sense and be useful to someone locally.

Jakub

[1] Scalable Authoritative OWL Reasoning for the Web, Aidan Hogan,
Andreas Harth, Axel Polleres, DERI Technical Report 2009-04-21, page 14
http://www.deri.ie/fileadmin/documents/DERI-TR-2009-04-21.pdf


> 
>    Henry
> 
> 
> 
>> Best
>> Bernhard
> 
> 
> 
Received on Friday, 9 July 2010 09:43:14 UTC

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