Re: ISSUE-30: How does SPARQL's notion of RDF dataset relate our notion of multiple graphs?

On Apr 17, 2011, at 10:07 , Dan Brickley wrote:

> On 17 April 2011 00:53, Richard Cyganiak <richard@cyganiak.de> wrote:
>> Pat,
>> 
>> On 16 Apr 2011, at 22:50, Pat Hayes wrote:
>>>> This part of SPARQL is successful and useful despite being disconnected from the RDF Model Theory. RDF Datasets as they are defined in SPARQL have no impact on entailments, and therefore do not require a relation to the RDF Model Theory.
>>> 
>>> The model theory is the semantics of RDF.
>> 
>> Yes, that's what it says on top of the document.
>> 
>>> It bears on any operation on RDF that is sensitive to the meanings of URIs or triples or literals. It is not purely concerned with entailments.
>> 
>> What operations, beside inference, are you talking about?
>> 
>> My understanding is that the RDF Model Theory exists to define which inferences are valid, given an RDF graph. What other purpose does it serve?
> 
> It helps us understand the kinds of transformations on RDF graph data
> that are truth-preserving, also the kinds that change the meaning of
> the graph such that the derrived graph says something different about
> the world. You can think of those in terms of entailments I guess; the
> mistake is to think 'I'm not writing a rule engine, so I can ignore
> that mathsy spec".

+1.

And... let us not use 'inference' as some sort of a dirty word. The RDF Semantics will tell me such trivially-looking-thing like the meaning of rdfs:subpropertyOf. If one looks at the RDF(S) entailment rules in the document, they all are, in fact, fairly trivial, but a specification must specify those somewhere. Whether a specific program just codes in that simple rule for subporpertyOf (and I am sure that happens all over the place!) or employs a full inference engine for the whole of the RDF Semantics is, in this sense, besides the point...

Ivan


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Ivan Herman, W3C Semantic Web Activity Lead
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