W3C home > Mailing lists > Public > public-rdf-wg@w3.org > September 2012

Re: Draft for a "minimal dataset semantics"

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 18 Sep 2012 14:53:00 -0500
Cc: public-rdf-wg@w3.org
Message-Id: <480FB656-EA40-4B18-A4B6-F2A2C0D65396@ihmc.us>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>

On Sep 14, 2012, at 10:21 AM, Antoine Zimmermann wrote:

....

>>> To me, it is important to have entailment between datasets.
>>> 
>>> { <n,G> } entails { <n,G'> }
>>> 
>>> is not the same as "extract G from <n,G>, G entails G'".
>>> 
>>> I want that the inferred triples are labeled by the graph IRI, for
>>> various purposes including version management, provenance management,
>>> temporal validity, etc.
>>> 
>> [pfps:] I don't see what you get from this beyond entailment between RDF graphs.
>> If, however, the WG ends up with some definition of entailment between
>> RDF datasets, I much prefer a direct relationship between the IRI and
>> the graph.
> 
> You get entailment between <name,graph> pairs. One of the things that I want to be able to do is materialise inferences over a dataset and claim "the dataset I build is known to be semantically equivalent to the original dataset, by virtue of the W3C approved dataset semantics".

Well, right now you can, for example, say that the graphs in your dataset are semantically equivalent to the corresponding (ie same "name") ones in the original one. Why isn't that enough?  And someone else can say that every graph in his dataset is equivalent to at least one graph in the original, and someone else can say that all the graphs in the original are equivalent to some graph in his, and so on. And all of you are quite clear and unambiguous, and everyone knows exactly what you mean. (Well, everyone who actually reads things, that is. I am excluding "casual" users.)

> If you say nothing, then there can be different behaviours, such as: extract the graph from the <n,g> pair, apply forward chaining inference an put back those inference inside a freshly named graph.

We cannot legislate against behaviors. Semantics does not prohibit any behavior.

> 
> This is something you may want to do inside your system, and it's fine, but if you expose the result to the world in a TriG file, there is no way to understand the relation between the truth of graph in a <name,graph> pair, and the inferred triples that may or may not exist in a different pair.

Well, surely that relation is simply one of the graph entailments. Why would the presence of a name paired with a graph change what the graph entails? I can put a graph next to an elephant, and its still the same graph. 

> There's also the argument relative to semantic extensions of the dataset semantics for dealing with certain cases. To specify an extension, you need at least a base semantics. Otherwise it's just yet another semantics from scratch.
> There are very strong connections between the dataset semantics, however simple it may be, and contextual logics.

There could be, if we were to pursue that idea, cf. http://www.w3.org/2011/rdf-wg/wiki/AnotherSpin  

Pat

> 
> 
> --AZ
> 
>> 
>> peter
>> 
>> 
>> 
> 
> -- 
> Antoine Zimmermann
> ISCOD / LSTI - Institut Henri Fayol
> École Nationale Supérieure des Mines de Saint-Étienne
> 158 cours Fauriel
> 42023 Saint-Étienne Cedex 2
> France
> Tél:+33(0)4 77 42 66 03
> Fax:+33(0)4 77 42 66 66
> http://zimmer.aprilfoolsreview.com/
> 
> 

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Received on Tuesday, 18 September 2012 19:53:34 GMT

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